From 256d50e85520c6bbd00480287eae89023b14de73 Mon Sep 17 00:00:00 2001
From: Thomas Citharel <tcit@tcit.fr>
Date: Thu, 14 Feb 2019 14:19:55 +0100
Subject: [PATCH] Allow tag relations + bump ecto deps

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
---
 config/dev.exs                                |   1 -
 config/prod.exs                               |   1 -
 config/test.exs                               |   1 -
 lib/mobilizon/actors/actors.ex                |   2 +-
 lib/mobilizon/actors/service/activation.ex    |   7 +-
 .../actors/service/reset_password.ex          |   2 +-
 lib/mobilizon/actors/service/tools.ex         |   5 +-
 lib/mobilizon/actors/user.ex                  |   9 +-
 lib/mobilizon/events/event.ex                 |   6 +-
 lib/mobilizon/events/events.ex                | 107 +++++++++++++++++-
 lib/mobilizon/events/session.ex               |   4 +-
 lib/mobilizon/events/tag.ex                   |   2 +
 lib/mobilizon/events/tag_relations.ex         |  41 +++++++
 lib/mobilizon/postgrex_types.ex               |   2 +-
 lib/mobilizon/repo.ex                         |   4 +-
 lib/mobilizon_web/auth_error_handler.ex       |   2 +-
 lib/mobilizon_web/endpoint.ex                 |   2 +-
 lib/mobilizon_web/resolvers/tag.ex            |  40 +++++++
 lib/mobilizon_web/schema/event.ex             |   8 +-
 lib/mobilizon_web/schema/tag.ex               |  30 +++++
 lib/service/activity_pub/activity_pub.ex      |   5 +-
 lib/service/activity_pub/utils.ex             |   2 +-
 lib/service/federator.ex                      |   2 +-
 mix.exs                                       |  17 ++-
 mix.lock                                      |  42 ++++---
 .../20190208141700_tags_relations.exs         |  22 ++++
 .../20190214100858_drop_datetimetz.exs        |  48 ++++++++
 priv/repo/seeds.exs                           |  24 ++--
 test/fixtures/mastodon-delete.json            |   9 +-
 test/mobilizon/actors/actors_test.exs         |   2 +-
 test/mobilizon/events/events_test.exs         |  95 ++++++++++++++--
 .../activity_pub/transmogrifier_test.exs      |  80 ++++++-------
 .../activity_pub_controller_test.exs          |   2 +-
 .../resolvers/event_resolver_test.exs         |   6 +-
 .../resolvers/participant_resolver_test.exs   |   2 +-
 .../resolvers/user_resolver_test.exs          |   4 +-
 test/support/factory.ex                       |   9 +-
 37 files changed, 515 insertions(+), 132 deletions(-)
 create mode 100644 lib/mobilizon/events/tag_relations.ex
 create mode 100644 lib/mobilizon_web/resolvers/tag.ex
 create mode 100644 lib/mobilizon_web/schema/tag.ex
 create mode 100644 priv/repo/migrations/20190208141700_tags_relations.exs
 create mode 100644 priv/repo/migrations/20190214100858_drop_datetimetz.exs

diff --git a/config/dev.exs b/config/dev.exs
index 3c90c9d3d..824b6e886 100644
--- a/config/dev.exs
+++ b/config/dev.exs
@@ -57,7 +57,6 @@ config :mobilizon, Mobilizon.Mailer, adapter: Bamboo.LocalAdapter
 
 # Configure your database
 config :mobilizon, Mobilizon.Repo,
-  adapter: Ecto.Adapters.Postgres,
   types: Mobilizon.PostgresTypes,
   username: System.get_env("MOBILIZON_DATABASE_USERNAME") || "mobilizon",
   password: System.get_env("MOBILIZON_DATABASE_PASSWORD") || "mobilizon",
diff --git a/config/prod.exs b/config/prod.exs
index 5820f0f7c..3cea69df6 100644
--- a/config/prod.exs
+++ b/config/prod.exs
@@ -28,7 +28,6 @@ config :mobilizon, MobilizonWeb.Endpoint,
 
 # Configure your database
 config :mobilizon, Mobilizon.Repo,
-  adapter: Ecto.Adapters.Postgres,
   types: Mobilizon.PostgresTypes,
   username: System.get_env("MOBILIZON_DATABASE_USERNAME") || "mobilizon",
   password: System.get_env("MOBILIZON_DATABASE_PASSWORD") || "mobilizon",
diff --git a/config/test.exs b/config/test.exs
index c6aee32d6..c906f42e8 100644
--- a/config/test.exs
+++ b/config/test.exs
@@ -20,7 +20,6 @@ config :logger,
 
 # Configure your database
 config :mobilizon, Mobilizon.Repo,
-  adapter: Ecto.Adapters.Postgres,
   types: Mobilizon.PostgresTypes,
   username: System.get_env("MOBILIZON_DATABASE_USERNAME") || "mobilizon",
   password: System.get_env("MOBILIZON_DATABASE_PASSWORD") || "mobilizon",
diff --git a/lib/mobilizon/actors/actors.ex b/lib/mobilizon/actors/actors.ex
index 084f4be6c..9118899c8 100644
--- a/lib/mobilizon/actors/actors.ex
+++ b/lib/mobilizon/actors/actors.ex
@@ -579,7 +579,7 @@ defmodule Mobilizon.Actors do
   """
   def authenticate(%{user: user, password: password}) do
     # Does password match the one stored in the database?
-    case Comeonin.Argon2.checkpw(password, user.password_hash) do
+    case Argon2.verify_pass(password, user.password_hash) do
       true ->
         # Yes, create and return the token
         MobilizonWeb.Guardian.encode_and_sign(user)
diff --git a/lib/mobilizon/actors/service/activation.ex b/lib/mobilizon/actors/service/activation.ex
index b94e6501f..250d16340 100644
--- a/lib/mobilizon/actors/service/activation.ex
+++ b/lib/mobilizon/actors/service/activation.ex
@@ -12,7 +12,7 @@ defmodule Mobilizon.Actors.Service.Activation do
     with %User{} = user <- Actors.get_user_by_activation_token(token),
          {:ok, %User{} = user} <-
            Actors.update_user(user, %{
-             "confirmed_at" => DateTime.utc_now(),
+             "confirmed_at" => DateTime.utc_now() |> DateTime.truncate(:second),
              "confirmation_sent_at" => nil,
              "confirmation_token" => nil
            }) do
@@ -26,7 +26,10 @@ defmodule Mobilizon.Actors.Service.Activation do
 
   def resend_confirmation_email(%User{} = user, locale \\ "en") do
     with :ok <- Tools.we_can_send_email(user, :confirmation_sent_at),
-         {:ok, user} <- Actors.update_user(user, %{"confirmation_sent_at" => DateTime.utc_now()}) do
+         {:ok, user} <-
+           Actors.update_user(user, %{
+             "confirmation_sent_at" => DateTime.utc_now() |> DateTime.truncate(:second)
+           }) do
       send_confirmation_email(user, locale)
       Logger.info("Sent confirmation email again to #{user.email}")
       {:ok, user.email}
diff --git a/lib/mobilizon/actors/service/reset_password.ex b/lib/mobilizon/actors/service/reset_password.ex
index cd5fe478a..f6604fba1 100644
--- a/lib/mobilizon/actors/service/reset_password.ex
+++ b/lib/mobilizon/actors/service/reset_password.ex
@@ -43,7 +43,7 @@ defmodule Mobilizon.Actors.Service.ResetPassword do
            Repo.update(
              User.send_password_reset_changeset(user, %{
                "reset_password_token" => Tools.random_string(30),
-               "reset_password_sent_at" => DateTime.utc_now()
+               "reset_password_sent_at" => DateTime.utc_now() |> DateTime.truncate(:second)
              })
            ) do
       mail =
diff --git a/lib/mobilizon/actors/service/tools.ex b/lib/mobilizon/actors/service/tools.ex
index 39ff2a0f5..2383cd7e3 100644
--- a/lib/mobilizon/actors/service/tools.ex
+++ b/lib/mobilizon/actors/service/tools.ex
@@ -11,7 +11,10 @@ defmodule Mobilizon.Actors.Service.Tools do
         :ok
 
       _ ->
-        case Timex.before?(Timex.shift(Map.get(user, key), hours: 1), DateTime.utc_now()) do
+        case Timex.before?(
+               Timex.shift(Map.get(user, key), hours: 1),
+               DateTime.utc_now() |> DateTime.truncate(:second)
+             ) do
           true ->
             :ok
 
diff --git a/lib/mobilizon/actors/user.ex b/lib/mobilizon/actors/user.ex
index da36a3540..780581698 100644
--- a/lib/mobilizon/actors/user.ex
+++ b/lib/mobilizon/actors/user.ex
@@ -89,7 +89,12 @@ defmodule Mobilizon.Actors.User do
     case changeset do
       %Ecto.Changeset{valid?: true, changes: %{email: _email}} ->
         changeset = put_change(changeset, :confirmation_token, random_string(30))
-        put_change(changeset, :confirmation_sent_at, DateTime.utc_now())
+
+        put_change(
+          changeset,
+          :confirmation_sent_at,
+          DateTime.utc_now() |> DateTime.truncate(:second)
+        )
 
       _ ->
         changeset
@@ -122,7 +127,7 @@ defmodule Mobilizon.Actors.User do
         put_change(
           changeset,
           :password_hash,
-          Comeonin.Argon2.hashpwsalt(password)
+          Argon2.hash_pwd_salt(password)
         )
 
       _ ->
diff --git a/lib/mobilizon/events/event.ex b/lib/mobilizon/events/event.ex
index d795f40c6..98a82876f 100644
--- a/lib/mobilizon/events/event.ex
+++ b/lib/mobilizon/events/event.ex
@@ -32,16 +32,16 @@ defmodule Mobilizon.Events.Event do
   schema "events" do
     field(:url, :string)
     field(:local, :boolean, default: true)
-    field(:begins_on, Timex.Ecto.DateTimeWithTimezone)
+    field(:begins_on, :utc_datetime)
     field(:description, :string)
-    field(:ends_on, Timex.Ecto.DateTimeWithTimezone)
+    field(:ends_on, :utc_datetime)
     field(:title, :string)
     field(:status, Mobilizon.Events.EventStatusEnum, default: :confirmed)
     field(:visibility, Mobilizon.Events.EventVisibilityEnum, default: :public)
     field(:join_options, Mobilizon.Events.JoinOptionsEnum, default: :free)
     field(:thumbnail, :string)
     field(:large_image, :string)
-    field(:publish_at, Timex.Ecto.DateTimeWithTimezone)
+    field(:publish_at, :utc_datetime)
     field(:uuid, Ecto.UUID, default: Ecto.UUID.generate())
     field(:online_address, :string)
     field(:phone_address, :string)
diff --git a/lib/mobilizon/events/events.ex b/lib/mobilizon/events/events.ex
index e0c9bc137..ae81caf7a 100644
--- a/lib/mobilizon/events/events.ex
+++ b/lib/mobilizon/events/events.ex
@@ -458,8 +458,32 @@ defmodule Mobilizon.Events do
       [%Tag{}, ...]
 
   """
-  def list_tags do
-    Repo.all(Tag)
+  def list_tags(page \\ nil, limit \\ nil) do
+    Repo.all(
+      Tag
+      |> paginate(page, limit)
+    )
+  end
+
+  @doc """
+  Returns the list of tags for an event.
+
+  ## Examples
+
+      iex> list_tags_for_event(id)
+      [%Participant{}, ...]
+
+  """
+  def list_tags_for_event(id, page \\ nil, limit \\ nil) do
+    Repo.all(
+      from(
+        t in Tag,
+        join: e in "events_tags",
+        on: t.id == e.tag_id,
+        where: e.event_id == ^id
+      )
+      |> paginate(page, limit)
+    )
   end
 
   @doc """
@@ -543,6 +567,85 @@ defmodule Mobilizon.Events do
     Tag.changeset(tag, %{})
   end
 
+  alias Mobilizon.Events.TagRelation
+
+  @doc """
+  Create a relation between two tags
+  """
+  def create_tag_relation(attrs \\ {}) do
+    %TagRelation{}
+    |> TagRelation.changeset(attrs)
+    |> Repo.insert(conflict_target: [:tag_id, :link_id], on_conflict: [inc: [weight: 1]])
+  end
+
+  @doc """
+  Remove a tag relation
+  """
+  def delete_tag_relation(%TagRelation{} = tag_relation) do
+    Repo.delete(tag_relation)
+  end
+
+  @doc """
+  Returns whether two tags are linked or not
+  """
+  def are_tags_linked(%Tag{id: tag1_id}, %Tag{id: tag2_id}) do
+    case from(tr in TagRelation,
+           where: tr.tag_id == ^min(tag1_id, tag2_id) and tr.link_id == ^max(tag1_id, tag2_id)
+         )
+         |> Repo.one() do
+      %TagRelation{} -> true
+      _ -> false
+    end
+  end
+
+  @doc """
+  Returns the tags neighbors for a given tag
+
+  We can't rely on the single many_to_many relation since we also want tags that link to our tag, not just tags linked by this one
+
+  The SQL query looks like this:
+  ```sql
+  SELECT * FROM tags t
+  RIGHT JOIN (
+    SELECT weight, link_id AS id
+    FROM tag_relations t2
+    WHERE tag_id = 1
+    UNION ALL
+    SELECT tag_id AS id, weight
+    FROM tag_relations t2
+    WHERE link_id = 1
+  ) tr
+  ON t.id = tr.id
+  ORDER BY tr.weight
+  DESC;
+  ```
+  """
+  def tag_neighbors(%Tag{id: id}, relation_minimum \\ 1, limit \\ 10) do
+    query2 =
+      from(tr in TagRelation,
+        select: %{id: tr.tag_id, weight: tr.weight},
+        where: tr.link_id == ^id
+      )
+
+    query =
+      from(tr in TagRelation,
+        select: %{id: tr.link_id, weight: tr.weight},
+        union_all: ^query2,
+        where: tr.tag_id == ^id
+      )
+
+    final_query =
+      from(t in Tag,
+        right_join: q in subquery(query),
+        on: [id: t.id],
+        where: q.weight >= ^relation_minimum,
+        limit: ^limit,
+        order_by: [desc: q.weight]
+      )
+
+    Repo.all(final_query)
+  end
+
   alias Mobilizon.Events.Participant
 
   @doc """
diff --git a/lib/mobilizon/events/session.ex b/lib/mobilizon/events/session.ex
index 178670f2a..5f03ec00e 100644
--- a/lib/mobilizon/events/session.ex
+++ b/lib/mobilizon/events/session.ex
@@ -15,8 +15,8 @@ defmodule Mobilizon.Events.Session do
     field(:subtitle, :string)
     field(:title, :string)
     field(:videos_urls, :string)
-    field(:begins_on, Timex.Ecto.DateTimeWithTimezone)
-    field(:ends_on, Timex.Ecto.DateTimeWithTimezone)
+    field(:begins_on, :utc_datetime)
+    field(:ends_on, :utc_datetime)
     belongs_to(:event, Event)
     belongs_to(:track, Track)
 
diff --git a/lib/mobilizon/events/tag.ex b/lib/mobilizon/events/tag.ex
index 79ac2b523..fafcfe157 100644
--- a/lib/mobilizon/events/tag.ex
+++ b/lib/mobilizon/events/tag.ex
@@ -39,10 +39,12 @@ defmodule Mobilizon.Events.Tag do
   import Ecto.Changeset
   alias Mobilizon.Events.Tag
   alias Mobilizon.Events.Tag.TitleSlug
+  alias Mobilizon.Events.TagRelation
 
   schema "tags" do
     field(:title, :string)
     field(:slug, TitleSlug.Type)
+    many_to_many(:related_tags, Tag, join_through: TagRelation)
 
     timestamps()
   end
diff --git a/lib/mobilizon/events/tag_relations.ex b/lib/mobilizon/events/tag_relations.ex
new file mode 100644
index 000000000..65618cb19
--- /dev/null
+++ b/lib/mobilizon/events/tag_relations.ex
@@ -0,0 +1,41 @@
+defmodule Mobilizon.Events.TagRelation do
+  @moduledoc """
+  Represents a tag for events
+  """
+  use Ecto.Schema
+  import Ecto.Changeset
+  alias Mobilizon.Events.Tag
+  alias Mobilizon.Events.TagRelation
+
+  @primary_key false
+  schema "tag_relations" do
+    belongs_to(:tag, Tag, primary_key: true)
+    belongs_to(:link, Tag, primary_key: true)
+    field(:weight, :integer, default: 1)
+  end
+
+  @doc false
+  def changeset(%TagRelation{} = tag, attrs) do
+    changeset =
+      tag
+      |> cast(attrs, [:tag_id, :link_id, :weight])
+      |> validate_required([:tag_id, :link_id])
+
+    # Return if tag_id or link_id are not set because it will fail later otherwise
+    with %Ecto.Changeset{errors: []} <- changeset do
+      changes = changeset.changes
+
+      changeset =
+        changeset
+        |> put_change(:tag_id, min(changes.tag_id, changes.link_id))
+        |> put_change(:link_id, max(changes.tag_id, changes.link_id))
+
+      changeset
+      |> unique_constraint(:tag_id, name: :tag_relations_pkey)
+      |> check_constraint(:tag_id,
+        name: :no_self_loops_check,
+        message: "Can't add a relation on self"
+      )
+    end
+  end
+end
diff --git a/lib/mobilizon/postgrex_types.ex b/lib/mobilizon/postgrex_types.ex
index 0ff906637..d06805578 100644
--- a/lib/mobilizon/postgrex_types.ex
+++ b/lib/mobilizon/postgrex_types.ex
@@ -1,5 +1,5 @@
 Postgrex.Types.define(
   Mobilizon.PostgresTypes,
   [Geo.PostGIS.Extension] ++ Ecto.Adapters.Postgres.extensions(),
-  json: Poison
+  json: Jason
 )
diff --git a/lib/mobilizon/repo.ex b/lib/mobilizon/repo.ex
index 1ce8c576b..d25e5b21b 100644
--- a/lib/mobilizon/repo.ex
+++ b/lib/mobilizon/repo.ex
@@ -2,7 +2,9 @@ defmodule Mobilizon.Repo do
   @moduledoc """
   Mobilizon Repo
   """
-  use Ecto.Repo, otp_app: :mobilizon
+  use Ecto.Repo,
+    otp_app: :mobilizon,
+    adapter: Ecto.Adapters.Postgres
 
   @doc """
   Dynamically loads the repository url from the
diff --git a/lib/mobilizon_web/auth_error_handler.ex b/lib/mobilizon_web/auth_error_handler.ex
index fea3e6500..853ff92be 100644
--- a/lib/mobilizon_web/auth_error_handler.ex
+++ b/lib/mobilizon_web/auth_error_handler.ex
@@ -5,7 +5,7 @@ defmodule MobilizonWeb.AuthErrorHandler do
   import Plug.Conn
 
   def auth_error(conn, {type, _reason}, _opts) do
-    body = Poison.encode!(%{message: to_string(type)})
+    body = Jason.encode!(%{message: to_string(type)})
     send_resp(conn, 401, body)
   end
 end
diff --git a/lib/mobilizon_web/endpoint.ex b/lib/mobilizon_web/endpoint.ex
index 2b85a3d78..6717ee50d 100644
--- a/lib/mobilizon_web/endpoint.ex
+++ b/lib/mobilizon_web/endpoint.ex
@@ -40,7 +40,7 @@ defmodule MobilizonWeb.Endpoint do
     Plug.Parsers,
     parsers: [:urlencoded, :multipart, :json],
     pass: ["*/*"],
-    json_decoder: Poison
+    json_decoder: Jason
   )
 
   plug(Plug.MethodOverride)
diff --git a/lib/mobilizon_web/resolvers/tag.ex b/lib/mobilizon_web/resolvers/tag.ex
new file mode 100644
index 000000000..abc3861de
--- /dev/null
+++ b/lib/mobilizon_web/resolvers/tag.ex
@@ -0,0 +1,40 @@
+defmodule MobilizonWeb.Resolvers.Tag do
+  @moduledoc """
+  Handles the tag-related GraphQL calls
+  """
+  require Logger
+  alias Mobilizon.Events.Event
+  alias Mobilizon.Events.Tag
+
+  def list_tags(_parent, %{page: page, limit: limit}, _resolution) do
+    tags = Mobilizon.Events.list_tags(page, limit)
+
+    {:ok, tags}
+  end
+
+  @doc """
+  Retrieve the list of tags for an event
+  """
+  def list_tags_for_event(%Event{id: id}, _args, _resolution) do
+    {:ok, Mobilizon.Events.list_tags_for_event(id)}
+  end
+
+  @doc """
+  Retrieve the list of related tags for a given tag ID
+  """
+  def get_related_tags(_parent, %{tag_id: tag_id}, _resolution) do
+    with %Tag{} = tag <- Mobilizon.Events.get_tag!(tag_id),
+         tags <- Mobilizon.Events.tag_neighbors(tag) do
+      {:ok, tags}
+    end
+  end
+
+  @doc """
+  Retrieve the list of related tags for a parent tag
+  """
+  def get_related_tags(%Tag{} = tag, _args, _resolution) do
+    with tags <- Mobilizon.Events.tag_neighbors(tag) do
+      {:ok, tags}
+    end
+  end
+end
diff --git a/lib/mobilizon_web/schema/event.ex b/lib/mobilizon_web/schema/event.ex
index 70230463b..1214bf3a0 100644
--- a/lib/mobilizon_web/schema/event.ex
+++ b/lib/mobilizon_web/schema/event.ex
@@ -8,6 +8,7 @@ defmodule MobilizonWeb.Schema.EventType do
   import_types(MobilizonWeb.Schema.AddressType)
   import_types(MobilizonWeb.Schema.Events.ParticipantType)
   import_types(MobilizonWeb.Schema.Events.CategoryType)
+  import_types(MobilizonWeb.Schema.TagType)
   alias MobilizonWeb.Resolvers
 
   @desc "An event"
@@ -37,7 +38,12 @@ defmodule MobilizonWeb.Schema.EventType do
     )
 
     field(:attributed_to, :actor, description: "Who the event is attributed to (often a group)")
-    # field(:tags, list_of(:tag))
+
+    field(:tags, list_of(:tag),
+      resolve: &MobilizonWeb.Resolvers.Tag.list_tags_for_event/3,
+      description: "The event's tags"
+    )
+
     field(:category, :category, description: "The event's category")
 
     field(:participants, list_of(:participant),
diff --git a/lib/mobilizon_web/schema/tag.ex b/lib/mobilizon_web/schema/tag.ex
new file mode 100644
index 000000000..7c4237ccd
--- /dev/null
+++ b/lib/mobilizon_web/schema/tag.ex
@@ -0,0 +1,30 @@
+defmodule MobilizonWeb.Schema.TagType do
+  @moduledoc """
+  Schema representation for Tags
+  """
+  use Absinthe.Schema.Notation
+  alias MobilizonWeb.Resolvers
+
+  @desc "A tag"
+  object :tag do
+    field(:id, :id, description: "The tag's ID")
+    field(:slug, :string, description: "The tags's slug")
+    field(:title, :string, description: "The tag's title")
+
+    field(
+      :related,
+      list_of(:tag),
+      resolve: &Resolvers.Tag.get_related_tags/3,
+      description: "Related tags to this tag"
+    )
+  end
+
+  object :tag_queries do
+    @desc "Get the list of tags"
+    field :tags, non_null(list_of(:tag)) do
+      arg(:page, :integer, default_value: 1)
+      arg(:limit, :integer, default_value: 10)
+      resolve(&Resolvers.Tag.list_tags/3)
+    end
+  end
+end
diff --git a/lib/service/activity_pub/activity_pub.ex b/lib/service/activity_pub/activity_pub.ex
index 662096ab6..d94701cb4 100644
--- a/lib/service/activity_pub/activity_pub.ex
+++ b/lib/service/activity_pub/activity_pub.ex
@@ -495,7 +495,10 @@ defmodule Mobilizon.Service.ActivityPub do
             ical_events =
               body
               |> ExIcal.parse()
-              |> ExIcal.by_range(DateTime.utc_now(), DateTime.utc_now() |> Timex.shift(years: 1))
+              |> ExIcal.by_range(
+                DateTime.utc_now(),
+                DateTime.utc_now() |> DateTime.truncate(:second) |> Timex.shift(years: 1)
+              )
 
             activities =
               ical_events
diff --git a/lib/service/activity_pub/utils.ex b/lib/service/activity_pub/utils.ex
index a24ceff08..0c243054f 100644
--- a/lib/service/activity_pub/utils.ex
+++ b/lib/service/activity_pub/utils.ex
@@ -46,7 +46,7 @@ defmodule Mobilizon.Service.ActivityPub.Utils do
   end
 
   def make_date do
-    DateTime.utc_now() |> DateTime.to_iso8601()
+    DateTime.utc_now() |> DateTime.truncate(:second) |> DateTime.to_iso8601()
   end
 
   @doc """
diff --git a/lib/service/federator.ex b/lib/service/federator.ex
index 968a37552..161d36707 100644
--- a/lib/service/federator.ex
+++ b/lib/service/federator.ex
@@ -59,7 +59,7 @@ defmodule Mobilizon.Service.Federator do
       _e ->
         # Just drop those for now
         Logger.error("Unhandled activity")
-        Logger.error(Poison.encode!(params, pretty: 2))
+        Logger.error(Jason.encode!(params))
     end
   end
 
diff --git a/mix.exs b/mix.exs
index 5a746e2d2..1b40ed4e1 100644
--- a/mix.exs
+++ b/mix.exs
@@ -51,27 +51,25 @@ defmodule Mobilizon.Mixfile do
     [
       {:phoenix, "~> 1.4.0"},
       {:phoenix_pubsub, "~> 1.0"},
-      {:phoenix_ecto, "~> 3.2"},
+      {:phoenix_ecto, "~> 4.0"},
       {:postgrex, ">= 0.0.0"},
       {:phoenix_html, "~> 2.10"},
       {:gettext, "~> 0.11"},
-      {:cowboy, "~> 1.0"},
+      {:cowboy, "~> 2.6"},
       {:guardian, "~> 1.2"},
-      {:guardian_db, "~> 1.1"},
-      {:comeonin, "~> 4.0"},
-      {:argon2_elixir, "~> 1.2"},
+      {:guardian_db, "~> 2.0"},
+      {:argon2_elixir, "~> 2.0"},
       {:cors_plug, "~> 2.0"},
       {:ecto_autoslug_field, "~> 1.0"},
       {:rsa_ex, "~> 0.1"},
       {:geo, "~> 3.0"},
-      {:geo_postgis, "~> 2.0"},
+      {:geo_postgis, "~> 3.1"},
       {:timex, "~> 3.0"},
-      {:timex_ecto, "~> 3.0"},
       {:icalendar, "~> 0.6"},
       {:exgravatar, "~> 2.0.1"},
       {:httpoison, "~> 1.0"},
       {:json_ld, "~> 0.3"},
-      {:jason, "~> 1.0"},
+      {:jason, "~> 1.1"},
       {:ex_crypto, "~> 0.9.0"},
       {:http_sign, "~> 0.1.1"},
       {:ecto_enum, "~> 1.0"},
@@ -82,12 +80,11 @@ defmodule Mobilizon.Mixfile do
       {:absinthe, "~> 1.4.0"},
       {:absinthe_phoenix, "~> 1.4.0"},
       {:absinthe_plug, "~> 1.4.0"},
-      {:poison, "~> 3.1"},
       {:absinthe_ecto, "~> 0.1.3"},
       {:dataloader, "~> 1.0"},
       {:arc, "~> 0.11.0"},
       {:arc_ecto, "~> 0.11.0"},
-      {:plug_cowboy, "~> 1.0"},
+      {:plug_cowboy, "~> 2.0"},
       # Dev and test dependencies
       {:phoenix_live_reload, "~> 1.2", only: :dev},
       {:ex_machina, "~> 2.2", only: [:dev, :test]},
diff --git a/mix.lock b/mix.lock
index 60cfd13e9..eb532ec3f 100644
--- a/mix.lock
+++ b/mix.lock
@@ -5,30 +5,30 @@
   "absinthe_plug": {:hex, :absinthe_plug, "1.4.6", "ac5d2d3d02acf52fda0f151b294017ab06e2ed1c6c15334e06aac82c94e36e08", [:mix], [{:absinthe, "~> 1.4.11", [hex: :absinthe, repo: "hexpm", optional: false]}, {:plug, "~> 1.3.2 or ~> 1.4", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "arc": {:hex, :arc, "0.11.0", "ac7a0cc03035317b6fef9fe94c97d7d9bd183a3e7ce1606aa0c175cfa8d1ba6d", [:mix], [{:ex_aws, "~> 2.0", [hex: :ex_aws, repo: "hexpm", optional: true]}, {:ex_aws_s3, "~> 2.0", [hex: :ex_aws_s3, repo: "hexpm", optional: true]}, {:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:poison, "~> 2.2 or ~> 3.1", [hex: :poison, repo: "hexpm", optional: true]}, {:sweet_xml, "~> 0.6", [hex: :sweet_xml, repo: "hexpm", optional: true]}], "hexpm"},
   "arc_ecto": {:hex, :arc_ecto, "0.11.1", "27aedf8c236b2097eed09d96f4ae73b43eb4c042a0e2ae42d44bf644cf16115c", [:mix], [{:arc, "~> 0.11.0", [hex: :arc, repo: "hexpm", optional: false]}, {:ecto, "~> 2.1 or ~> 3.0", [hex: :ecto, repo: "hexpm", optional: false]}], "hexpm"},
-  "argon2_elixir": {:hex, :argon2_elixir, "1.3.3", "487ffa071ef78c51d9b16e50ff3cf30cf8204e0aa4bdc8afd3765fdd8195e213", [:make, :mix], [{:elixir_make, "~> 0.4", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm"},
+  "argon2_elixir": {:hex, :argon2_elixir, "2.0.0", "e3539f441930d4c8296e36024168526626351c1f2c2df97cfd50f4e90b15386a", [:make, :mix], [{:comeonin, "~> 5.0", [hex: :comeonin, repo: "hexpm", optional: false]}, {:elixir_make, "~> 0.4", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm"},
   "bamboo": {:hex, :bamboo, "1.2.0", "8aebd24f7c606c32d0163c398004a11608ca1028182a169b2e527793bfab7561", [:mix], [{:hackney, ">= 1.13.0", [hex: :hackney, repo: "hexpm", optional: false]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}, {:poison, ">= 1.5.0", [hex: :poison, repo: "hexpm", optional: true]}], "hexpm"},
   "bamboo_smtp": {:hex, :bamboo_smtp, "1.6.0", "0a3607b77f22554af58c547350c1c73ebba6f4fb2c4bd0b11713ab5b4081588f", [:mix], [{:bamboo, "~> 1.0", [hex: :bamboo, repo: "hexpm", optional: false]}, {:gen_smtp, "~> 0.12.0", [hex: :gen_smtp, repo: "hexpm", optional: false]}], "hexpm"},
   "base64url": {:hex, :base64url, "0.0.1", "36a90125f5948e3afd7be97662a1504b934dd5dac78451ca6e9abf85a10286be", [:rebar], [], "hexpm"},
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
   "certifi": {:hex, :certifi, "2.4.2", "75424ff0f3baaccfd34b1214184b6ef616d89e420b258bb0a5ea7d7bc628f7f0", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
   "combine": {:hex, :combine, "0.10.0", "eff8224eeb56498a2af13011d142c5e7997a80c8f5b97c499f84c841032e429f", [:mix], [], "hexpm"},
-  "comeonin": {:hex, :comeonin, "4.1.2", "3eb5620fd8e35508991664b4c2b04dd41e52f1620b36957be837c1d7784b7592", [:mix], [{:argon2_elixir, "~> 1.2", [hex: :argon2_elixir, repo: "hexpm", optional: true]}, {:bcrypt_elixir, "~> 0.12.1 or ~> 1.0", [hex: :bcrypt_elixir, repo: "hexpm", optional: true]}, {:pbkdf2_elixir, "~> 0.12", [hex: :pbkdf2_elixir, repo: "hexpm", optional: true]}], "hexpm"},
+  "comeonin": {:hex, :comeonin, "5.0.0", "e87716d3b1c31e56312f6a1545a5548cdc80376cff5025fe3b12be2046934837", [:mix], [], "hexpm"},
   "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm"},
   "cors_plug": {:hex, :cors_plug, "2.0.0", "238ddb479f92b38f6dc1ae44b8d81f0387f9519101a6da442d543ab70ee0e482", [:mix], [{:plug, "~> 1.3 or ~> 1.4 or ~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
-  "cowboy": {:hex, :cowboy, "1.1.2", "61ac29ea970389a88eca5a65601460162d370a70018afe6f949a29dca91f3bb0", [:rebar3], [{:cowlib, "~> 1.0.2", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.3.2", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},
-  "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], [], "hexpm"},
+  "cowboy": {:hex, :cowboy, "2.6.1", "f2e06f757c337b3b311f9437e6e072b678fcd71545a7b2865bdaa154d078593f", [:rebar3], [{:cowlib, "~> 2.7.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.7.1", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},
+  "cowlib": {:hex, :cowlib, "2.7.0", "3ef16e77562f9855a2605900cedb15c1462d76fb1be6a32fc3ae91973ee543d2", [:rebar3], [], "hexpm"},
   "credo": {:hex, :credo, "1.0.2", "88bc918f215168bf6ce7070610a6173c45c82f32baa08bdfc80bf58df2d103b6", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
   "dataloader": {:hex, :dataloader, "1.0.6", "fb724d6d3fb6acb87d27e3b32dea3a307936ad2d245faf9cf5221d1323d6a4ba", [:mix], [{:ecto, ">= 0.0.0", [hex: :ecto, repo: "hexpm", optional: true]}], "hexpm"},
-  "db_connection": {:hex, :db_connection, "1.1.3", "89b30ca1ef0a3b469b1c779579590688561d586694a3ce8792985d4d7e575a61", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
-  "decimal": {:hex, :decimal, "1.6.0", "bfd84d90ff966e1f5d4370bdd3943432d8f65f07d3bab48001aebd7030590dcc", [:mix], [], "hexpm"},
+  "db_connection": {:hex, :db_connection, "2.0.5", "ddb2ba6761a08b2bb9ca0e7d260e8f4dd39067426d835c24491a321b7f92a4da", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}], "hexpm"},
+  "decimal": {:hex, :decimal, "1.7.0", "30d6b52c88541f9a66637359ddf85016df9eb266170d53105f02e4a67e00c5aa", [:mix], [], "hexpm"},
   "dialyxir": {:hex, :dialyxir, "1.0.0-rc.4", "71b42f5ee1b7628f3e3a6565f4617dfb02d127a0499ab3e72750455e986df001", [:mix], [{:erlex, "~> 0.1", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm"},
   "earmark": {:hex, :earmark, "1.3.1", "73812f447f7a42358d3ba79283cfa3075a7580a3a2ed457616d6517ac3738cb9", [:mix], [], "hexpm"},
-  "ecto": {:hex, :ecto, "2.2.11", "4bb8f11718b72ba97a2696f65d247a379e739a0ecabf6a13ad1face79844791c", [:mix], [{:db_connection, "~> 1.1", [hex: :db_connection, repo: "hexpm", optional: true]}, {:decimal, "~> 1.2", [hex: :decimal, repo: "hexpm", optional: false]}, {:mariaex, "~> 0.8.0", [hex: :mariaex, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}, {:poolboy, "~> 1.5", [hex: :poolboy, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.13.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:sbroker, "~> 1.0", [hex: :sbroker, repo: "hexpm", optional: true]}], "hexpm"},
+  "ecto": {:hex, :ecto, "3.0.7", "44dda84ac6b17bbbdeb8ac5dfef08b7da253b37a453c34ab1a98de7f7e5fec7f", [:mix], [{:decimal, "~> 1.6", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}], "hexpm"},
   "ecto_autoslug_field": {:hex, :ecto_autoslug_field, "1.0.0", "577eed25e6d045b8d783f82c9872f97c3a84017a4feae50eaf3cf4e1334a19e2", [:mix], [{:ecto, ">= 2.1.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:slugger, ">= 0.2.0", [hex: :slugger, repo: "hexpm", optional: false]}], "hexpm"},
   "ecto_enum": {:hex, :ecto_enum, "1.2.0", "9ead3ee04efc4cb68a50560a9d9ebb665dd697f957f1c3df8e81bf863cf7a4e9", [:mix], [{:ecto, ">= 2.0.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:mariaex, ">= 0.0.0", [hex: :mariaex, repo: "hexpm", optional: true]}, {:postgrex, ">= 0.0.0", [hex: :postgrex, repo: "hexpm", optional: true]}], "hexpm"},
-  "elixir_make": {:hex, :elixir_make, "0.5.0", "3d65ce6d537d2ce164c0311551a607b90ea7f91d85242a67f3c5e59693c3aa50", [:mix], [], "hexpm"},
-  "email_checker": {:hex, :email_checker, "0.1.2", "05b3121c71b69f1ab5df7d8b4844046898bf218031998ef53f20c6b8bfd219e9", [:mix], [{:socket, "~> 0.3.1", [hex: :socket, repo: "hexpm", optional: false]}], "hexpm"},
-  "erlex": {:hex, :erlex, "0.2.0", "80349ebd58553dbd63489937380bfa7d906be3266b91bbd9d2bd6b71f1e8c07d", [:mix], [], "hexpm"},
+  "ecto_sql": {:hex, :ecto_sql, "3.0.5", "7e44172b4f7aca4469f38d7f6a3da394dbf43a1bcf0ca975e958cb957becd74e", [:mix], [{:db_connection, "~> 2.0", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.0.6", [hex: :ecto, repo: "hexpm", optional: false]}, {:mariaex, "~> 0.9.1", [hex: :mariaex, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.14.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.3.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm"},
+  "elixir_make": {:hex, :elixir_make, "0.5.2", "96a28c79f5b8d34879cd95ebc04d2a0d678cfbbd3e74c43cb63a76adf0ee8054", [:mix], [], "hexpm"},
+  "erlex": {:hex, :erlex, "0.2.1", "cee02918660807cbba9a7229cae9b42d1c6143b768c781fa6cee1eaf03ad860b", [:mix], [], "hexpm"},
   "ex_crypto": {:hex, :ex_crypto, "0.9.0", "e04a831034c4d0a43fb2858f696d6b5ae0f87f07dedca3452912fd3cb5ee3ca2", [:mix], [{:poison, ">= 2.0.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "ex_doc": {:hex, :ex_doc, "0.19.3", "3c7b0f02851f5fc13b040e8e925051452e41248f685e40250d7e40b07b9f8c10", [:mix], [{:earmark, "~> 1.2", [hex: :earmark, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.10", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm"},
   "ex_ical": {:hex, :ex_ical, "0.2.0", "4b928b554614704016cc0c9ee226eb854da9327a1cc460457621ceacb1ac29a6", [:mix], [{:timex, "~> 3.1", [hex: :timex, repo: "hexpm", optional: false]}], "hexpm"},
@@ -42,11 +42,11 @@
   "file_system": {:hex, :file_system, "0.2.6", "fd4dc3af89b9ab1dc8ccbcc214a0e60c41f34be251d9307920748a14bf41f1d3", [:mix], [], "hexpm"},
   "gen_smtp": {:hex, :gen_smtp, "0.12.0", "97d44903f5ca18ca85cb39aee7d9c77e98d79804bbdef56078adcf905cb2ef00", [:rebar3], [], "hexpm"},
   "geo": {:hex, :geo, "3.1.0", "727e005262430d037e870ff364e65d80ca5ca21d5ac8eddd57a1ada72c3f83b0", [:mix], [], "hexpm"},
-  "geo_postgis": {:hex, :geo_postgis, "2.1.0", "e0640d18276cb1dd58aeae3f5eed9a61641a5110901e1e35d0d662031d936b33", [:mix], [{:geo, "~> 3.0", [hex: :geo, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0", [hex: :poison, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.13", [hex: :postgrex, repo: "hexpm", optional: false]}], "hexpm"},
+  "geo_postgis": {:hex, :geo_postgis, "3.1.0", "d06c8fa5fd140a52a5c9dab4ad6623a696dd7d99dd791bb361d3f94942442ff9", [:mix], [{:geo, "~> 3.1", [hex: :geo, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:poison, "~> 2.2 or ~> 3.0 or ~> 4.0", [hex: :poison, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.14", [hex: :postgrex, repo: "hexpm", optional: false]}], "hexpm"},
   "geolix": {:hex, :geolix, "0.17.0", "8f3f4068be08599912de67ae24372a6c148794a0152f9f83ffd5a2ffcb21d29a", [:mix], [{:mmdb2_decoder, "~> 0.3.0", [hex: :mmdb2_decoder, repo: "hexpm", optional: false]}, {:poolboy, "~> 1.0", [hex: :poolboy, repo: "hexpm", optional: false]}], "hexpm"},
   "gettext": {:hex, :gettext, "0.16.1", "e2130b25eebcbe02bb343b119a07ae2c7e28bd4b146c4a154da2ffb2b3507af2", [:mix], [], "hexpm"},
   "guardian": {:hex, :guardian, "1.2.1", "bdc8dd3dbf0fb7216cb6f91c11831faa1a64d39cdaed9a611e37f2413e584983", [:mix], [{:jose, "~> 1.8", [hex: :jose, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.3", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, "~> 1.3.3 or ~> 1.4", [hex: :plug, repo: "hexpm", optional: true]}], "hexpm"},
-  "guardian_db": {:hex, :guardian_db, "1.1.0", "45ab94206cce38f7443dc27de6dc52966ccbdeff65ca1b1f11a6d8f3daceb556", [:mix], [{:ecto, "~> 2.2", [hex: :ecto, repo: "hexpm", optional: false]}, {:guardian, "~> 1.0", [hex: :guardian, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.13", [hex: :postgrex, repo: "hexpm", optional: true]}], "hexpm"},
+  "guardian_db": {:hex, :guardian_db, "2.0.0", "65019ee9e09e1cfc157c0ec7840747bc54959ed4b985da80fecae9ff19b0f5df", [:mix], [{:ecto, "~> 3.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:ecto_sql, "~> 3.0.0", [hex: :ecto_sql, repo: "hexpm", optional: false]}, {:guardian, "~> 1.0", [hex: :guardian, repo: "hexpm", optional: false]}, {:postgrex, "~> 0.13", [hex: :postgrex, repo: "hexpm", optional: true]}], "hexpm"},
   "hackney": {:hex, :hackney, "1.15.0", "287a5d2304d516f63e56c469511c42b016423bcb167e61b611f6bad47e3ca60e", [:rebar3], [{:certifi, "2.4.2", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.4", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
   "http_sign": {:hex, :http_sign, "0.1.1", "b16edb83aa282892f3271f9a048c155e772bf36e15700ab93901484c55f8dd10", [:mix], [{:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "httpoison": {:hex, :httpoison, "1.5.0", "71ae9f304bdf7f00e9cd1823f275c955bdfc68282bc5eb5c85c3a9ade865d68e", [:mix], [{:hackney, "~> 1.8", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
@@ -56,8 +56,6 @@
   "jose": {:hex, :jose, "1.9.0", "4167c5f6d06ffaebffd15cdb8da61a108445ef5e85ab8f5a7ad926fdf3ada154", [:mix, :rebar3], [{:base64url, "~> 0.0.1", [hex: :base64url, repo: "hexpm", optional: false]}], "hexpm"},
   "json_ld": {:hex, :json_ld, "0.3.0", "92f508ca831b9e4530e3e6c950976fdafcf26323e6817c325b3e1ee78affc4bd", [:mix], [{:jason, "~> 1.1.1", [hex: :jason, repo: "hexpm", optional: false]}, {:rdf, "~> 0.5", [hex: :rdf, repo: "hexpm", optional: false]}], "hexpm"},
   "jsx": {:hex, :jsx, "2.8.3", "a05252d381885240744d955fbe3cf810504eb2567164824e19303ea59eef62cf", [:mix, :rebar3], [], "hexpm"},
-  "kronky": {:hex, :kronky, "0.5.0", "b2038c267f02b297044cb574f542fa96763278a88b32a97d0c37bde95c63c13b", [:mix], [{:absinthe, "~> 1.3", [hex: :absinthe, repo: "hexpm", optional: false]}, {:ecto, ">= 2.1.4", [hex: :ecto, repo: "hexpm", optional: false]}], "hexpm"},
-  "littlefinger": {:hex, :littlefinger, "0.1.0", "5d3720bebd65d6a2051c31ca45f28b2d452d25aeeb8adb0a8f87013868bb0e7e", [:mix], [{:httpoison, "~> 1.0", [hex: :httpoison, repo: "hexpm", optional: false]}, {:poison, "~> 3.1", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "makeup": {:hex, :makeup, "0.8.0", "9cf32aea71c7fe0a4b2e9246c2c4978f9070257e5c9ce6d4a28ec450a839b55f", [:mix], [{:nimble_parsec, "~> 0.5.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm"},
   "makeup_elixir": {:hex, :makeup_elixir, "0.13.0", "be7a477997dcac2e48a9d695ec730b2d22418292675c75aa2d34ba0909dcdeda", [:mix], [{:makeup, "~> 0.8", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm"},
   "meck": {:hex, :meck, "0.8.13", "ffedb39f99b0b99703b8601c6f17c7f76313ee12de6b646e671e3188401f7866", [:rebar3], [], "hexpm"},
@@ -68,26 +66,24 @@
   "mmdb2_decoder": {:hex, :mmdb2_decoder, "0.3.0", "03a159a52342d3328cf2b774f1036e56719f7edc7f919180588a7764854c3318", [:mix], [], "hexpm"},
   "nimble_parsec": {:hex, :nimble_parsec, "0.5.0", "90e2eca3d0266e5c53f8fbe0079694740b9c91b6747f2b7e3c5d21966bba8300", [:mix], [], "hexpm"},
   "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm"},
-  "phoenix": {:hex, :phoenix, "1.4.0", "56fe9a809e0e735f3e3b9b31c1b749d4b436e466d8da627b8d82f90eaae714d2", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 1.0 or ~> 2.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}], "hexpm"},
-  "phoenix_ecto": {:hex, :phoenix_ecto, "3.6.0", "d65dbcedd6af568d8582dcd7da516c3051016bad51f9953e5337fea40bcd8a9d", [:mix], [{:ecto, "~> 2.2", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.9", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
+  "phoenix": {:hex, :phoenix, "1.4.1", "801f9d632808657f1f7c657c8bbe624caaf2ba91429123ebe3801598aea4c3d9", [:mix], [{:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:phoenix_pubsub, "~> 1.1", [hex: :phoenix_pubsub, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}, {:plug_cowboy, "~> 1.0 or ~> 2.0", [hex: :plug_cowboy, repo: "hexpm", optional: true]}], "hexpm"},
+  "phoenix_ecto": {:hex, :phoenix_ecto, "4.0.0", "c43117a136e7399ea04ecaac73f8f23ee0ffe3e07acfcb8062fe5f4c9f0f6531", [:mix], [{:ecto, "~> 3.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:phoenix_html, "~> 2.9", [hex: :phoenix_html, repo: "hexpm", optional: true]}, {:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_html": {:hex, :phoenix_html, "2.13.1", "fa8f034b5328e2dfa0e4131b5569379003f34bc1fafdaa84985b0b9d2f12e68b", [:mix], [{:plug, "~> 1.5", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_live_reload": {:hex, :phoenix_live_reload, "1.2.0", "3bb31a9fbd40ffe8652e60c8660dffd72dd231efcdf49b744fb75b9ef7db5dd2", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}, {:phoenix, "~> 1.4", [hex: :phoenix, repo: "hexpm", optional: false]}], "hexpm"},
   "phoenix_pubsub": {:hex, :phoenix_pubsub, "1.1.1", "6668d787e602981f24f17a5fbb69cc98f8ab085114ebfac6cc36e10a90c8e93c", [:mix], [], "hexpm"},
-  "plug": {:hex, :plug, "1.7.1", "8516d565fb84a6a8b2ca722e74e2cd25ca0fc9d64f364ec9dbec09d33eb78ccd", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}], "hexpm"},
-  "plug_cowboy": {:hex, :plug_cowboy, "1.0.0", "2e2a7d3409746d335f451218b8bb0858301c3de6d668c3052716c909936eb57a", [:mix], [{:cowboy, "~> 1.0", [hex: :cowboy, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
+  "plug": {:hex, :plug, "1.7.2", "d7b7db7fbd755e8283b6c0a50be71ec0a3d67d9213d74422d9372effc8e87fd1", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}], "hexpm"},
+  "plug_cowboy": {:hex, :plug_cowboy, "2.0.1", "d798f8ee5acc86b7d42dbe4450b8b0dadf665ce588236eb0a751a132417a980e", [:mix], [{:cowboy, "~> 2.5", [hex: :cowboy, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "plug_crypto": {:hex, :plug_crypto, "1.0.0", "18e49317d3fa343f24620ed22795ec29d4a5e602d52d1513ccea0b07d8ea7d4d", [:mix], [], "hexpm"},
   "poison": {:hex, :poison, "3.1.0", "d9eb636610e096f86f25d9a46f35a9facac35609a7591b3be3326e99a0484665", [:mix], [], "hexpm"},
   "poolboy": {:hex, :poolboy, "1.5.2", "392b007a1693a64540cead79830443abf5762f5d30cf50bc95cb2c1aaafa006b", [:rebar3], [], "hexpm"},
-  "postgrex": {:hex, :postgrex, "0.13.5", "3d931aba29363e1443da167a4b12f06dcd171103c424de15e5f3fc2ba3e6d9c5", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 1.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.0", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm"},
-  "ranch": {:hex, :ranch, "1.3.2", "e4965a144dc9fbe70e5c077c65e73c57165416a901bd02ea899cfd95aa890986", [:rebar3], [], "hexpm"},
+  "postgrex": {:hex, :postgrex, "0.14.1", "63247d4a5ad6b9de57a0bac5d807e1c32d41e39c04b8a4156a26c63bcd8a2e49", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.0", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm"},
+  "ranch": {:hex, :ranch, "1.7.1", "6b1fab51b49196860b733a49c07604465a47bdb78aa10c1c16a3d199f7f8c881", [:rebar3], [], "hexpm"},
   "rdf": {:hex, :rdf, "0.5.4", "57e09d4adfe7646fe0c3514b703b76eaf29d537b250b36abae75e66d7e5920cf", [:mix], [{:decimal, "~> 1.5", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm"},
   "rsa_ex": {:hex, :rsa_ex, "0.4.0", "e28dd7dc5236e156df434af0e4aa822384c8866c928e17b785d4edb7c253b558", [:mix], [], "hexpm"},
   "slugger": {:hex, :slugger, "0.3.0", "efc667ab99eee19a48913ccf3d038b1fb9f165fa4fbf093be898b8099e61b6ed", [:mix], [], "hexpm"},
-  "socket": {:hex, :socket, "0.3.13", "98a2ab20ce17f95fb512c5cadddba32b57273e0d2dba2d2e5f976c5969d0c632", [:mix], [], "hexpm"},
   "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.4", "f0eafff810d2041e93f915ef59899c923f4568f4585904d010387ed74988e77b", [:make, :mix, :rebar3], [], "hexpm"},
+  "telemetry": {:hex, :telemetry, "0.3.0", "099a7f3ce31e4780f971b4630a3c22ec66d22208bc090fe33a2a3a6a67754a73", [:rebar3], [], "hexpm"},
   "timex": {:hex, :timex, "3.5.0", "b0a23167da02d0fe4f1a4e104d1f929a00d348502b52432c05de875d0b9cffa5", [:mix], [{:combine, "~> 0.10", [hex: :combine, repo: "hexpm", optional: false]}, {:gettext, "~> 0.10", [hex: :gettext, repo: "hexpm", optional: false]}, {:tzdata, "~> 0.1.8 or ~> 0.5", [hex: :tzdata, repo: "hexpm", optional: false]}], "hexpm"},
-  "timex_ecto": {:hex, :timex_ecto, "3.3.0", "d5bdef09928e7a60f10a0baa47ce653f29b43d6fee87b30b236b216d0e36b98d", [:mix], [{:ecto, "~> 2.2", [hex: :ecto, repo: "hexpm", optional: false]}, {:timex, "~> 3.1", [hex: :timex, repo: "hexpm", optional: false]}], "hexpm"},
   "tzdata": {:hex, :tzdata, "0.5.19", "7962a3997bf06303b7d1772988ede22260f3dae1bf897408ebdac2b4435f4e6a", [:mix], [{:hackney, "~> 1.0", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
   "unicode_util_compat": {:hex, :unicode_util_compat, "0.4.1", "d869e4c68901dd9531385bb0c8c40444ebf624e60b6962d95952775cac5e90cd", [:rebar3], [], "hexpm"},
-  "uuid": {:hex, :uuid, "1.1.8", "e22fc04499de0de3ed1116b770c7737779f226ceefa0badb3592e64d5cfb4eb9", [:mix], [], "hexpm"},
 }
diff --git a/priv/repo/migrations/20190208141700_tags_relations.exs b/priv/repo/migrations/20190208141700_tags_relations.exs
new file mode 100644
index 000000000..e9d745719
--- /dev/null
+++ b/priv/repo/migrations/20190208141700_tags_relations.exs
@@ -0,0 +1,22 @@
+defmodule Mobilizon.Repo.Migrations.TagsRelations do
+  use Ecto.Migration
+
+  def up do
+    create table(:tag_relations, primary_key: false) do
+      add :tag_id, references(:tags, on_delete: :delete_all), null: false, primary_key: true
+      add :link_id, references(:tags, on_delete: :delete_all), null: false, primary_key: true
+      add :weight, :integer, null: false, default: 1
+    end
+    create constraint(:tag_relations, :no_self_loops_check, check: "tag_id <> link_id")
+    create index(:tag_relations, [:tag_id], name: :index_tag_relations_tag_id)
+    create index(:tag_relations, [:link_id], name: :index_tag_relations_link_id)
+  end
+
+  def down do
+    drop constraint(:tag_relations, :no_self_loops_check)
+
+    drop index(:tag_relations, [:tags_id])
+    drop index(:tag_relations, [:link_id])
+    drop table(:tag_relations)
+  end
+end
diff --git a/priv/repo/migrations/20190214100858_drop_datetimetz.exs b/priv/repo/migrations/20190214100858_drop_datetimetz.exs
new file mode 100644
index 000000000..8515375bd
--- /dev/null
+++ b/priv/repo/migrations/20190214100858_drop_datetimetz.exs
@@ -0,0 +1,48 @@
+defmodule Mobilizon.Repo.Migrations.DropDatetimetz do
+  use Ecto.Migration
+
+  def up do
+    alter table(:events) do
+      remove(:begins_on)
+      remove(:ends_on)
+      remove(:publish_at)
+      add(:begins_on, :utc_datetime)
+      add(:ends_on, :utc_datetime)
+      add(:publish_at, :utc_datetime)
+    end
+
+    alter table(:sessions) do
+      remove(:begins_on)
+      remove(:ends_on)
+      add(:begins_on, :utc_datetime)
+      add(:ends_on, :utc_datetime)
+    end
+
+    execute "DROP TYPE datetimetz"
+  end
+
+  def down do
+    execute("""
+    CREATE TYPE datetimetz AS (
+        dt timestamptz,
+        tz varchar
+    );
+    """)
+
+    alter table(:events) do
+      remove(:begins_on)
+      remove(:ends_on)
+      remove(:publish_at)
+      add(:begins_on, :datetimetz)
+      add(:ends_on, :datetimetz)
+      add(:publish_at, :datetimetz)
+    end
+
+    alter table(:sessions) do
+      remove(:begins_on)
+      remove(:ends_on)
+      add(:begins_on, :datetimetz)
+      add(:ends_on, :datetimetz)
+    end
+  end
+end
diff --git a/priv/repo/seeds.exs b/priv/repo/seeds.exs
index b1ccb7bb6..62d3f430f 100644
--- a/priv/repo/seeds.exs
+++ b/priv/repo/seeds.exs
@@ -21,17 +21,21 @@ actor = insert(:actor, user: user)
 # Insert a second actor account for the same user
 actor2 = insert(:actor, user: user)
 
-# Make actor organize a few events
-event = insert(:event, organizer_actor: actor)
-event2 = insert(:event, organizer_actor: actor)
-event3 = insert(:event, organizer_actor: actor)
-event4 = insert(:event, organizer_actor: actor2)
+tag1 = insert(:tag)
+tag2 = insert(:tag)
+tag3 = insert(:tag)
 
-participant = insert(:participant, actor: actor, event: event, role: 4)
-participant = insert(:participant, actor: actor, event: event2, role: 4)
-participant = insert(:participant, actor: actor, event: event3, role: 4)
-participant = insert(:participant, actor: actor2, event: event4, role: 4)
-participant = insert(:participant, actor: actor, event: event4, role: 1)
+# Make actor organize a few events
+event = insert(:event, organizer_actor: actor, tags: [tag1, tag2])
+event2 = insert(:event, organizer_actor: actor, tags: [tag1, tag2])
+event3 = insert(:event, organizer_actor: actor, tags: [tag1])
+event4 = insert(:event, organizer_actor: actor2, tags: [tag3, tag2])
+
+insert(:participant, actor: actor, event: event, role: :creator)
+insert(:participant, actor: actor, event: event2, role: :creator)
+insert(:participant, actor: actor, event: event3, role: :creator)
+insert(:participant, actor: actor2, event: event4, role: :creator)
+insert(:participant, actor: actor, event: event4, role: :participant)
 
 # Insert a group
 group = insert(:actor, type: :Group)
diff --git a/test/fixtures/mastodon-delete.json b/test/fixtures/mastodon-delete.json
index 87a582002..ab6265b5f 100644
--- a/test/fixtures/mastodon-delete.json
+++ b/test/fixtures/mastodon-delete.json
@@ -2,12 +2,9 @@
   "type": "Delete",
   "signature": {
     "type": "RsaSignature2017",
-    "signatureValue": "cw0RlfNREf+5VdsOYcCBDrv521eiLsDTAYNHKffjF0bozhCnOh+wHkFik7WamUk$
-uEiN4L2H6vPlGRprAZGRhEwgy+A7rIFQNmLrpW5qV5UNVI/2F7kngEHqZQgbQYj9hW+5GMYmPkHdv3D72ZefGw$
-4Xa2NBLGFpAjQllfzt7kzZLKKY2DM99FdUa64I2Wj3iD04Hs23SbrUdAeuGk/c1Cg6bwGNG4vxoiwn1jikgJLA$
-NAlSGjsRGdR7LfbC7GqWWsW3cSNsLFPoU6FyALjgTrrYoHiXe0QHggw+L3yMLfzB2S/L46/VRbyb+WDKMBIXUL$
-5owmzHSi6e/ZtCI3w==",
-    "creator": "http://mastodon.example.org/users/gargron#main-key",                       "created": "2018-03-03T16:24:11Z"
+    "signatureValue": "cw0RlfNREf+5VdsOYcCBDrv521eiLsDTAYNHKffjF0bozhCnOh+wHkFik7WamUkuEiN4L2H6vPlGRprAZGRhEwgy+A7rIFQNmLrpW5qV5UNVI/2F7kngEHqZQgbQYj9hW+5GMYmPkHdv3D72ZefGw4Xa2NBLGFpAjQllfzt7kzZLKKY2DM99FdUa64I2Wj3iD04Hs23SbrUdAeuGk/c1Cg6bwGNG4vxoiwn1jikgJLANAlSGjsRGdR7LfbC7GqWWsW3cSNsLFPoU6FyALjgTrrYoHiXe0QHggw+L3yMLfzB2S/L46/VRbyb+WDKMBIXUL5owmzHSi6e/ZtCI3w==",
+    "creator": "http://mastodon.example.org/users/gargron#main-key",
+    "created": "2018-03-03T16:24:11Z"
   },
   "object": {
     "type": "Tombstone",
diff --git a/test/mobilizon/actors/actors_test.exs b/test/mobilizon/actors/actors_test.exs
index 7e67d79d3..aa15715bf 100644
--- a/test/mobilizon/actors/actors_test.exs
+++ b/test/mobilizon/actors/actors_test.exs
@@ -373,7 +373,7 @@ defmodule Mobilizon.ActorsTest do
       assert {:error, :user_not_found} = Actors.get_user_by_email(@email, true)
 
       Actors.update_user(user, %{
-        "confirmed_at" => DateTime.utc_now(),
+        "confirmed_at" => DateTime.utc_now() |> DateTime.truncate(:second),
         "confirmation_sent_at" => nil,
         "confirmation_token" => nil
       })
diff --git a/test/mobilizon/events/events_test.exs b/test/mobilizon/events/events_test.exs
index d326da56e..0ecd530f0 100644
--- a/test/mobilizon/events/events_test.exs
+++ b/test/mobilizon/events/events_test.exs
@@ -6,9 +6,9 @@ defmodule Mobilizon.EventsTest do
   alias Mobilizon.Events
 
   @event_valid_attrs %{
-    begins_on: "2010-04-17 14:00:00.000000Z",
+    begins_on: "2010-04-17 14:00:00Z",
     description: "some description",
-    ends_on: "2010-04-17 14:00:00.000000Z",
+    ends_on: "2010-04-17 14:00:00Z",
     title: "some title",
     url: "some url",
     uuid: "b5126423-f1af-43e4-a923-002a03003ba4"
@@ -24,15 +24,15 @@ defmodule Mobilizon.EventsTest do
     end
 
     @valid_attrs %{
-      begins_on: "2010-04-17 14:00:00.000000Z",
+      begins_on: "2010-04-17 14:00:00Z",
       description: "some description",
-      ends_on: "2010-04-17 14:00:00.000000Z",
+      ends_on: "2010-04-17 14:00:00Z",
       title: "some title"
     }
     @update_attrs %{
-      begins_on: "2011-05-18 15:01:01.000000Z",
+      begins_on: "2011-05-18 15:01:01Z",
       description: "some updated description",
-      ends_on: "2011-05-18 15:01:01.000000Z",
+      ends_on: "2011-05-18 15:01:01Z",
       title: "some updated title"
     }
     @invalid_attrs %{begins_on: nil, description: nil, ends_on: nil, title: nil}
@@ -90,9 +90,9 @@ defmodule Mobilizon.EventsTest do
         |> Map.put(:address_id, address.id)
 
       with {:ok, %Event{} = event} <- Events.create_event(valid_attrs) do
-        assert event.begins_on == DateTime.from_naive!(~N[2010-04-17 14:00:00.000000Z], "Etc/UTC")
+        assert event.begins_on == DateTime.from_naive!(~N[2010-04-17 14:00:00Z], "Etc/UTC")
         assert event.description == "some description"
-        assert event.ends_on == DateTime.from_naive!(~N[2010-04-17 14:00:00.000000Z], "Etc/UTC")
+        assert event.ends_on == DateTime.from_naive!(~N[2010-04-17 14:00:00Z], "Etc/UTC")
         assert event.title == "some title"
       else
         err ->
@@ -107,9 +107,9 @@ defmodule Mobilizon.EventsTest do
     test "update_event/2 with valid data updates the event", %{event: event} do
       assert {:ok, event} = Events.update_event(event, @update_attrs)
       assert %Event{} = event
-      assert event.begins_on == DateTime.from_naive!(~N[2011-05-18 15:01:01.000000Z], "Etc/UTC")
+      assert event.begins_on == DateTime.from_naive!(~N[2011-05-18 15:01:01Z], "Etc/UTC")
       assert event.description == "some updated description"
-      assert event.ends_on == DateTime.from_naive!(~N[2011-05-18 15:01:01.000000Z], "Etc/UTC")
+      assert event.ends_on == DateTime.from_naive!(~N[2011-05-18 15:01:01Z], "Etc/UTC")
       assert event.title == "some updated title"
     end
 
@@ -302,6 +302,81 @@ defmodule Mobilizon.EventsTest do
     end
   end
 
+  describe "tags_relations" do
+    alias Mobilizon.Events.TagRelation
+    alias Mobilizon.Events.Tag
+
+    setup do
+      tag1 = insert(:tag)
+      tag2 = insert(:tag)
+      {:ok, tag1: tag1, tag2: tag2}
+    end
+
+    test "create_tag_relation/1 with valid data creates a tag relation", %{
+      tag1: %Tag{id: tag1_id} = tag1,
+      tag2: %Tag{id: tag2_id} = tag2
+    } do
+      assert {:ok, %TagRelation{} = tag_relation} =
+               Events.create_tag_relation(%{tag_id: tag1_id, link_id: tag2_id})
+
+      assert Events.are_tags_linked(tag1, tag2)
+      assert Events.are_tags_linked(tag2, tag1)
+    end
+
+    test "create_tag_relation/1 with invalid data returns error changeset", %{
+      tag1: %Tag{} = tag1,
+      tag2: %Tag{} = tag2
+    } do
+      assert {:error, %Ecto.Changeset{}} =
+               Events.create_tag_relation(%{tag_id: nil, link_id: nil})
+
+      refute Events.are_tags_linked(tag1, tag2)
+    end
+
+    test "delete_tag_relation/1 deletes the tag relation" do
+      tag_relation = insert(:tag_relation)
+      assert {:ok, %TagRelation{}} = Events.delete_tag_relation(tag_relation)
+    end
+
+    test "tag_neighbors/2 return the connected tags for a given tag", %{
+      tag1: %Tag{} = tag1,
+      tag2: %Tag{} = tag2
+    } do
+      tag3 = insert(:tag)
+      tag4 = insert(:tag)
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag1.id, link_id: tag2.id})
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag2.id, link_id: tag1.id})
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag3.id, link_id: tag2.id})
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag4.id, link_id: tag1.id})
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag4.id, link_id: tag1.id})
+
+      assert {:ok, %TagRelation{}} =
+               Events.create_tag_relation(%{tag_id: tag4.id, link_id: tag1.id})
+
+      assert {:error,
+              %Ecto.Changeset{
+                errors: [
+                  tag_id:
+                    {"Can't add a relation on self",
+                     [constraint: :check, constraint_name: "no_self_loops_check"]}
+                ]
+              }} = Events.create_tag_relation(%{tag_id: tag1.id, link_id: tag1.id})
+
+      # The order is preserved, since tag4 has one more relation than tag2
+      assert [tag4, tag2] == Events.tag_neighbors(tag1)
+    end
+  end
+
   describe "participants" do
     alias Mobilizon.Events.{Participant, Event}
     alias Mobilizon.Actors.Actor
diff --git a/test/mobilizon/service/activity_pub/transmogrifier_test.exs b/test/mobilizon/service/activity_pub/transmogrifier_test.exs
index 450321cf2..a7dde3749 100644
--- a/test/mobilizon/service/activity_pub/transmogrifier_test.exs
+++ b/test/mobilizon/service/activity_pub/transmogrifier_test.exs
@@ -34,7 +34,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   data =
     #     File.read!("test/fixtures/mastodon-post-activity.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", activity["object"])
 
     #   {:ok, returned_activity} = Transmogrifier.handle_incoming(data)
@@ -45,7 +45,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     # test "it fetches replied-to activities if we don't have them" do
     #   data =
     #     File.read!("test/fixtures/mastodon-post-activity.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
 
     #   object =
     #     data["object"]
@@ -69,7 +69,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     # end
 
     test "it works for incoming notices" do
-      data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()
+      data = File.read!("test/fixtures/mastodon-post-activity.json") |> Jason.decode!()
 
       {:ok, %Mobilizon.Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -103,7 +103,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     end
 
     test "it works for incoming notices with hashtags" do
-      data = File.read!("test/fixtures/mastodon-post-activity-hashtag.json") |> Poison.decode!()
+      data = File.read!("test/fixtures/mastodon-post-activity-hashtag.json") |> Jason.decode!()
 
       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
       assert Enum.at(data["object"]["tag"], 2) == "moo"
@@ -111,7 +111,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #     test "it works for incoming notices with contentMap" do
     #       data =
-    #         File.read!("test/fixtures/mastodon-post-activity-contentmap.json") |> Poison.decode!()
+    #         File.read!("test/fixtures/mastodon-post-activity-contentmap.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -120,7 +120,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     #     end
 
     #     test "it works for incoming notices with to/cc not being an array (kroeg)" do
-    #       data = File.read!("test/fixtures/kroeg-post-activity.json") |> Poison.decode!()
+    #       data = File.read!("test/fixtures/kroeg-post-activity.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -129,7 +129,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     #     end
 
     #     test "it works for incoming announces with actor being inlined (kroeg)" do
-    #       data = File.read!("test/fixtures/kroeg-announce-with-inline-actor.json") |> Poison.decode!()
+    #       data = File.read!("test/fixtures/kroeg-announce-with-inline-actor.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -137,7 +137,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     #     end
 
     #     test "it works for incoming notices with tag not being an array (kroeg)" do
-    #       data = File.read!("test/fixtures/kroeg-array-less-emoji.json") |> Poison.decode!()
+    #       data = File.read!("test/fixtures/kroeg-array-less-emoji.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -145,7 +145,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     #                "icon_e_smile" => "https://puckipedia.com/forum/images/smilies/icon_e_smile.png"
     #              }
 
-    #       data = File.read!("test/fixtures/kroeg-array-less-hashtag.json") |> Poison.decode!()
+    #       data = File.read!("test/fixtures/kroeg-array-less-hashtag.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -153,7 +153,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     #     end
 
     test "it works for incoming notices with url not being a string (prismo)" do
-      data = File.read!("test/fixtures/prismo-url-map.json") |> Poison.decode!()
+      data = File.read!("test/fixtures/prismo-url-map.json") |> Jason.decode!()
 
       assert {:error, :not_supported} == Transmogrifier.handle_incoming(data)
       # Pages are not supported
@@ -167,7 +167,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
       data =
         File.read!("test/fixtures/mastodon-follow-activity.json")
-        |> Poison.decode!()
+        |> Jason.decode!()
         |> Map.put("object", actor.url)
 
       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -185,7 +185,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       data =
     #         File.read!("test/fixtures/hubzilla-follow-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", user.ap_id)
     #         |> Utils.normalize_params()
 
@@ -202,7 +202,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   data =
     #     File.read!("test/fixtures/mastodon-like.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", url)
 
     #   {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -218,7 +218,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   data =
     #     File.read!("test/fixtures/mastodon-undo-like.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", url)
 
     #   assert Transmogrifier.handle_incoming(data) == {:error, :not_supported}
@@ -229,14 +229,14 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   like_data =
     #     File.read!("test/fixtures/mastodon-like.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", comment.url)
 
     #   {:ok, %Activity{data: like_data, local: false}} = Transmogrifier.handle_incoming(like_data)
 
     #   data =
     #     File.read!("test/fixtures/mastodon-undo-like.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", like_data)
     #     |> Map.put("actor", like_data["actor"])
 
@@ -249,7 +249,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     # end
 
     # test "it works for incoming announces" do
-    #   data = File.read!("test/fixtures/mastodon-announce.json") |> Poison.decode!()
+    #   data = File.read!("test/fixtures/mastodon-announce.json") |> Jason.decode!()
 
     #   {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
 
@@ -270,7 +270,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   data =
     #     File.read!("test/fixtures/mastodon-announce.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", comment.url)
 
     #   {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -287,10 +287,10 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     # end
 
     test "it works for incoming update activities" do
-      data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()
+      data = File.read!("test/fixtures/mastodon-post-activity.json") |> Jason.decode!()
 
       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
-      update_data = File.read!("test/fixtures/mastodon-update.json") |> Poison.decode!()
+      update_data = File.read!("test/fixtures/mastodon-update.json") |> Jason.decode!()
 
       object =
         update_data["object"]
@@ -317,10 +317,10 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
     end
 
     #     test "it works for incoming update activities which lock the account" do
-    #       data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()
+    #       data = File.read!("test/fixtures/mastodon-post-activity.json") |> Jason.decode!()
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
-    #       update_data = File.read!("test/fixtures/mastodon-update.json") |> Poison.decode!()
+    #       update_data = File.read!("test/fixtures/mastodon-update.json") |> Jason.decode!()
 
     #       object =
     #         update_data["object"]
@@ -345,7 +345,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
       data =
         File.read!("test/fixtures/mastodon-delete.json")
-        |> Poison.decode!()
+        |> Jason.decode!()
 
       object =
         data["object"]
@@ -369,7 +369,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       data =
     #         File.read!("test/fixtures/mastodon-delete.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
 
     #       object =
     #         data["object"]
@@ -389,7 +389,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   announce_data =
     #     File.read!("test/fixtures/mastodon-announce.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", comment.url)
 
     #   {:ok, %Activity{data: announce_data, local: false}} =
@@ -397,7 +397,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #   data =
     #     File.read!("test/fixtures/mastodon-undo-announce.json")
-    #     |> Poison.decode!()
+    #     |> Jason.decode!()
     #     |> Map.put("object", announce_data)
     #     |> Map.put("actor", announce_data["actor"])
 
@@ -416,14 +416,14 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
       follow_data =
         File.read!("test/fixtures/mastodon-follow-activity.json")
-        |> Poison.decode!()
+        |> Jason.decode!()
         |> Map.put("object", actor.url)
 
       {:ok, %Activity{data: _, local: false}} = Transmogrifier.handle_incoming(follow_data)
 
       data =
         File.read!("test/fixtures/mastodon-unfollow-activity.json")
-        |> Poison.decode!()
+        |> Jason.decode!()
         |> Map.put("object", follow_data)
 
       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -442,7 +442,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       data =
     #         File.read!("test/fixtures/mastodon-block-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", user.ap_id)
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -462,7 +462,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       data =
     #         File.read!("test/fixtures/mastodon-block-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", blocked.ap_id)
     #         |> Map.put("actor", blocker.ap_id)
 
@@ -492,14 +492,14 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       block_data =
     #         File.read!("test/fixtures/mastodon-block-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", user.ap_id)
 
     #       {:ok, %Activity{data: _, local: false}} = Transmogrifier.handle_incoming(block_data)
 
     #       data =
     #         File.read!("test/fixtures/mastodon-unblock-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", block_data)
 
     #       {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
@@ -524,7 +524,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       accept_data =
     #         File.read!("test/fixtures/mastodon-accept-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
 
     #       object =
@@ -552,7 +552,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       accept_data =
     #         File.read!("test/fixtures/mastodon-accept-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
 
     #       accept_data =
@@ -574,7 +574,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       accept_data =
     #         File.read!("test/fixtures/mastodon-accept-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
     #         |> Map.put("object", follow_activity.data["id"])
 
@@ -592,7 +592,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       accept_data =
     #         File.read!("test/fixtures/mastodon-accept-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
 
     #       accept_data =
@@ -611,7 +611,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       accept_data =
     #         File.read!("test/fixtures/mastodon-reject-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
 
     #       accept_data =
@@ -635,7 +635,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       reject_data =
     #         File.read!("test/fixtures/mastodon-reject-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
 
     #       reject_data =
@@ -660,7 +660,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       reject_data =
     #         File.read!("test/fixtures/mastodon-reject-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("actor", followed.ap_id)
     #         |> Map.put("object", follow_activity.data["id"])
 
@@ -676,7 +676,7 @@ defmodule Mobilizon.Service.ActivityPub.TransmogrifierTest do
 
     #       data =
     #         File.read!("test/fixtures/mastodon-follow-activity.json")
-    #         |> Poison.decode!()
+    #         |> Jason.decode!()
     #         |> Map.put("object", user.ap_id)
     #         |> Map.put("id", "")
 
diff --git a/test/mobilizon_web/controllers/activity_pub_controller_test.exs b/test/mobilizon_web/controllers/activity_pub_controller_test.exs
index 3dfa42d95..0fe234fbc 100644
--- a/test/mobilizon_web/controllers/activity_pub_controller_test.exs
+++ b/test/mobilizon_web/controllers/activity_pub_controller_test.exs
@@ -82,7 +82,7 @@ defmodule MobilizonWeb.ActivityPubControllerTest do
   describe "/@:preferred_username/inbox" do
     test "it inserts an incoming event into the database", %{conn: conn} do
       use_cassette "activity_pub_controller/mastodon-post-activity_actor_call" do
-        data = File.read!("test/fixtures/mastodon-post-activity.json") |> Poison.decode!()
+        data = File.read!("test/fixtures/mastodon-post-activity.json") |> Jason.decode!()
 
         conn =
           conn
diff --git a/test/mobilizon_web/resolvers/event_resolver_test.exs b/test/mobilizon_web/resolvers/event_resolver_test.exs
index 2c1ee0b08..d43b1fca2 100644
--- a/test/mobilizon_web/resolvers/event_resolver_test.exs
+++ b/test/mobilizon_web/resolvers/event_resolver_test.exs
@@ -7,7 +7,7 @@ defmodule MobilizonWeb.Resolvers.EventResolverTest do
   @event %{
     description: "some body",
     title: "some title",
-    begins_on: Ecto.DateTime.utc(),
+    begins_on: DateTime.utc_now() |> DateTime.truncate(:second),
     uuid: "b5126423-f1af-43e4-a923-002a03003ba4",
     url: "some url"
   }
@@ -68,7 +68,9 @@ defmodule MobilizonWeb.Resolvers.EventResolverTest do
               createEvent(
                   title: "come to my event",
                   description: "it will be fine",
-                  begins_on: "#{DateTime.utc_now() |> DateTime.to_iso8601()}",
+                  begins_on: "#{
+        DateTime.utc_now() |> DateTime.truncate(:second) |> DateTime.to_iso8601()
+      }",
                   organizer_actor_id: "#{actor.id}",
                   category: "#{category.title}"
               ) {
diff --git a/test/mobilizon_web/resolvers/participant_resolver_test.exs b/test/mobilizon_web/resolvers/participant_resolver_test.exs
index ca5d0ddab..070d6c0c1 100644
--- a/test/mobilizon_web/resolvers/participant_resolver_test.exs
+++ b/test/mobilizon_web/resolvers/participant_resolver_test.exs
@@ -7,7 +7,7 @@ defmodule MobilizonWeb.Resolvers.ParticipantResolverTest do
   @event %{
     description: "some body",
     title: "some title",
-    begins_on: Ecto.DateTime.utc(),
+    begins_on: DateTime.utc_now() |> DateTime.truncate(:second),
     uuid: "b5126423-f1af-43e4-a923-002a03003ba4",
     url: "some url"
   }
diff --git a/test/mobilizon_web/resolvers/user_resolver_test.exs b/test/mobilizon_web/resolvers/user_resolver_test.exs
index 96c1f4cbd..e0cbd4525 100644
--- a/test/mobilizon_web/resolvers/user_resolver_test.exs
+++ b/test/mobilizon_web/resolvers/user_resolver_test.exs
@@ -477,7 +477,7 @@ defmodule MobilizonWeb.Resolvers.UserResolverTest do
 
       {:ok, %User{} = _user} =
         Actors.update_user(user, %{
-          "confirmed_at" => DateTime.utc_now(),
+          "confirmed_at" => DateTime.utc_now() |> DateTime.truncate(:second),
           "confirmation_sent_at" => nil,
           "confirmation_token" => nil
         })
@@ -509,7 +509,7 @@ defmodule MobilizonWeb.Resolvers.UserResolverTest do
 
       {:ok, %User{} = _user} =
         Actors.update_user(user, %{
-          "confirmed_at" => DateTime.utc_now(),
+          "confirmed_at" => DateTime.utc_now() |> DateTime.truncate(:second),
           "confirmation_sent_at" => nil,
           "confirmation_token" => nil
         })
diff --git a/test/support/factory.ex b/test/support/factory.ex
index 74537fff9..33075e4d0 100644
--- a/test/support/factory.ex
+++ b/test/support/factory.ex
@@ -10,7 +10,7 @@ defmodule Mobilizon.Factory do
       password_hash: "Jane Smith",
       email: sequence(:email, &"email-#{&1}@example.com"),
       role: 0,
-      confirmed_at: DateTime.utc_now(),
+      confirmed_at: DateTime.utc_now() |> DateTime.truncate(:second),
       confirmation_sent_at: nil,
       confirmation_token: nil
     }
@@ -67,6 +67,13 @@ defmodule Mobilizon.Factory do
     }
   end
 
+  def tag_relation_factory do
+    %Mobilizon.Events.TagRelation{
+      tag: build(:tag),
+      link: build(:tag)
+    }
+  end
+
   def address_factory do
     %Mobilizon.Addresses.Address{
       description: sequence("MyAddress"),