diff --git a/lib/mobilizon/actors/user.ex b/lib/mobilizon/actors/user.ex
index d69be537b..da36a3540 100644
--- a/lib/mobilizon/actors/user.ex
+++ b/lib/mobilizon/actors/user.ex
@@ -138,15 +138,10 @@ defmodule Mobilizon.Actors.User do
     {:ok, user}
   end
 
-  def owns_actor(%User{default_actor_id: default_actor_id}, %Actor{id: actor_id})
-      when default_actor_id == actor_id do
-    {:is_owned, true}
-  end
-
   def owns_actor(%User{actors: actors}, actor_id) do
-    case Enum.any?(actors, fn a -> a.id == actor_id end) do
-      true -> {:is_owned, true}
-      _ -> {:is_owned, false}
+    case Enum.find(actors, fn a -> a.id == actor_id end) do
+      nil -> {:is_owned, false}
+      actor -> {:is_owned, true, actor}
     end
   end
 end
diff --git a/lib/mobilizon/events/events.ex b/lib/mobilizon/events/events.ex
index 6cfb79c3c..e0c9bc137 100644
--- a/lib/mobilizon/events/events.ex
+++ b/lib/mobilizon/events/events.ex
@@ -582,6 +582,28 @@ defmodule Mobilizon.Events do
     )
   end
 
+  @doc """
+  Returns the list of organizers participants for an event.
+
+  ## Examples
+
+      iex> list_organizers_participants_for_event(id)
+      [%Participant{role: :creator}, ...]
+
+  """
+  def list_organizers_participants_for_event(id, page \\ nil, limit \\ nil) do
+    Repo.all(
+      from(
+        p in Participant,
+        join: e in Event,
+        on: p.event_id == e.id,
+        where: e.id == ^id and p.role == ^:creator,
+        preload: [:actor]
+      )
+      |> paginate(page, limit)
+    )
+  end
+
   @doc """
   Gets a single participant.
 
@@ -600,6 +622,16 @@ defmodule Mobilizon.Events do
     Repo.get_by!(Participant, event_id: event_id, actor_id: actor_id)
   end
 
+  @doc """
+  Get a single participant
+  """
+  def get_participant(event_id, actor_id) do
+    case Repo.get_by(Participant, event_id: event_id, actor_id: actor_id) do
+      nil -> {:error, :participant_not_found}
+      participant -> {:ok, participant}
+    end
+  end
+
   @doc """
   Creates a participant.
 
@@ -665,6 +697,18 @@ defmodule Mobilizon.Events do
     Participant.changeset(participant, %{})
   end
 
+  @doc """
+  Get the default participant role depending on the event join options
+  """
+  def get_default_participant_role(%Event{} = event) do
+    case event.join_options do
+      # Participant
+      :free -> :participant
+      # Not approved
+      _ -> :not_approved
+    end
+  end
+
   @doc """
   List event participation requests for an actor
   """
diff --git a/lib/mobilizon_web/resolvers/event.ex b/lib/mobilizon_web/resolvers/event.ex
index b11ba3831..74938c19d 100644
--- a/lib/mobilizon_web/resolvers/event.ex
+++ b/lib/mobilizon_web/resolvers/event.ex
@@ -4,7 +4,7 @@ defmodule MobilizonWeb.Resolvers.Event do
   """
   alias Mobilizon.Service.ActivityPub
   alias Mobilizon.Activity
-  alias Mobilizon.Events.Event
+  alias Mobilizon.Events.{Event, Participant}
   alias Mobilizon.Actors.User
 
   # We limit the max number of events that can be retrieved
@@ -43,6 +43,85 @@ defmodule MobilizonWeb.Resolvers.Event do
     {:ok, Mobilizon.Events.list_participants_for_event(uuid, 1, 10)}
   end
 
+  @doc """
+  Join an event for an actor
+  """
+  def actor_join_event(
+        _parent,
+        %{actor_id: actor_id, event_id: event_id},
+        %{
+          context: %{
+            current_user: user
+          }
+        }
+      ) do
+    with {:is_owned, true, actor} <- User.owns_actor(user, actor_id),
+         {:ok, %Event{} = event} <- Mobilizon.Events.get_event(event_id),
+         {:error, :participant_not_found} <- Mobilizon.Events.get_participant(event_id, actor_id),
+         role <- Mobilizon.Events.get_default_participant_role(event),
+         {:ok, participant} <-
+           Mobilizon.Events.create_participant(%{
+             role: role,
+             event_id: event.id,
+             actor_id: actor.id
+           }),
+         participant <-
+           Map.put(participant, :event, event)
+           |> Map.put(:actor, actor) do
+      {:ok, participant}
+    else
+      {:is_owned, false} ->
+        {:error, "Actor id is not owned by authenticated user"}
+
+      {:error, :event_not_found} ->
+        {:error, "Event id not found"}
+
+      {:ok, %Participant{}} ->
+        {:error, "You are already a participant of this event"}
+    end
+  end
+
+  def actor_join_event(_parent, _args, _resolution) do
+    {:error, "You need to be logged-in to join an event"}
+  end
+
+  @doc """
+  Leave an event for an actor
+  """
+  def actor_leave_event(
+        _parent,
+        %{actor_id: actor_id, event_id: event_id},
+        %{
+          context: %{
+            current_user: user
+          }
+        }
+      ) do
+    with {:is_owned, true, _} <- User.owns_actor(user, actor_id),
+         {:ok, %Participant{} = participant} <-
+           Mobilizon.Events.get_participant(event_id, actor_id),
+         {:only_organizer, false} <-
+           {:only_organizer,
+            Mobilizon.Events.list_organizers_participants_for_event(event_id) |> length == 1},
+         {:ok, _} <-
+           Mobilizon.Events.delete_participant(participant) do
+      {:ok, %{event: %{id: event_id}, actor: %{id: actor_id}}}
+    else
+      {:is_owned, false} ->
+        {:error, "Actor id is not owned by authenticated user"}
+
+      {:only_organizer, true} ->
+        {:error, "You can't leave event because you're the only event creator participant"}
+
+      {:error, :participant_not_found} ->
+        {:error, "Participant not found"}
+    end
+  end
+
+  def actor_leave_event(_parent, _args, _resolution) do
+    {:error, "You need to be logged-in to leave an event"}
+  end
+
   @doc """
   Search events by title
   """
@@ -103,7 +182,7 @@ defmodule MobilizonWeb.Resolvers.Event do
         context: %{current_user: user}
       }) do
     with {:ok, %Event{} = event} <- Mobilizon.Events.get_event(event_id),
-         {:is_owned, true} <- User.owns_actor(user, actor_id),
+         {:is_owned, true, _} <- User.owns_actor(user, actor_id),
          {:event_can_be_managed, true} <- Event.can_event_be_managed_by(event, actor_id),
          event <- Mobilizon.Events.delete_event!(event) do
       {:ok, %{id: event.id}}
diff --git a/lib/mobilizon_web/resolvers/group.ex b/lib/mobilizon_web/resolvers/group.ex
index b063691ae..5a698e2eb 100644
--- a/lib/mobilizon_web/resolvers/group.ex
+++ b/lib/mobilizon_web/resolvers/group.ex
@@ -82,7 +82,7 @@ defmodule MobilizonWeb.Resolvers.Group do
         }
       ) do
     with {:ok, %Actor{} = group} <- Actors.find_group_by_actor_id(group_id),
-         {:is_owned, true} <- User.owns_actor(user, actor_id),
+         {:is_owned, true, _} <- User.owns_actor(user, actor_id),
          {:ok, %Member{} = member} <- Member.get_member(actor_id, group.id),
          {:is_admin, true} <- Member.is_administrator(member),
          group <- Actors.delete_group!(group) do
diff --git a/lib/mobilizon_web/schema.ex b/lib/mobilizon_web/schema.ex
index 564522fe3..8ddc79e34 100644
--- a/lib/mobilizon_web/schema.ex
+++ b/lib/mobilizon_web/schema.ex
@@ -143,6 +143,7 @@ defmodule MobilizonWeb.Schema do
     import_fields(:event_mutations)
     import_fields(:category_mutations)
     import_fields(:comment_mutations)
+    import_fields(:participant_mutations)
 
     # @desc "Upload a picture"
     # field :upload_picture, :picture do
diff --git a/lib/mobilizon_web/schema/actor.ex b/lib/mobilizon_web/schema/actor.ex
index 757252042..76f36b6bf 100644
--- a/lib/mobilizon_web/schema/actor.ex
+++ b/lib/mobilizon_web/schema/actor.ex
@@ -12,7 +12,7 @@ defmodule MobilizonWeb.Schema.ActorInterface do
 
   @desc "An ActivityPub actor"
   interface :actor do
-    field(:id, :id, description: "Internal ID for this actor")
+    field(:id, :integer, description: "Internal ID for this actor")
     field(:url, :string, description: "The ActivityPub actor's URL")
     field(:type, :actor_type, description: "The type of Actor (Person, Group,…)")
     field(:name, :string, description: "The actor's displayed name")
diff --git a/lib/mobilizon_web/schema/actors/group.ex b/lib/mobilizon_web/schema/actors/group.ex
index 7a24382a9..365f58097 100644
--- a/lib/mobilizon_web/schema/actors/group.ex
+++ b/lib/mobilizon_web/schema/actors/group.ex
@@ -13,7 +13,7 @@ defmodule MobilizonWeb.Schema.Actors.GroupType do
   object :group do
     interfaces([:actor])
 
-    field(:id, :id, description: "Internal ID for this group")
+    field(:id, :integer, description: "Internal ID for this group")
     field(:url, :string, description: "The ActivityPub actor's URL")
     field(:type, :actor_type, description: "The type of Actor (Person, Group,…)")
     field(:name, :string, description: "The actor's displayed name")
diff --git a/lib/mobilizon_web/schema/actors/person.ex b/lib/mobilizon_web/schema/actors/person.ex
index 4397caf6e..2271c26fe 100644
--- a/lib/mobilizon_web/schema/actors/person.ex
+++ b/lib/mobilizon_web/schema/actors/person.ex
@@ -13,7 +13,7 @@ defmodule MobilizonWeb.Schema.Actors.PersonType do
   """
   object :person do
     interfaces([:actor])
-    field(:id, :id, description: "Internal ID for this person")
+    field(:id, :integer, description: "Internal ID for this person")
     field(:user, :user, description: "The user this actor is associated to")
 
     field(:member_of, list_of(:member), description: "The list of groups this person is member of")
diff --git a/lib/mobilizon_web/schema/event.ex b/lib/mobilizon_web/schema/event.ex
index 003dee4bf..70230463b 100644
--- a/lib/mobilizon_web/schema/event.ex
+++ b/lib/mobilizon_web/schema/event.ex
@@ -12,7 +12,7 @@ defmodule MobilizonWeb.Schema.EventType do
 
   @desc "An event"
   object :event do
-    field(:id, :id, description: "Internal ID for this event")
+    field(:id, :integer, description: "Internal ID for this event")
     field(:uuid, :uuid, description: "The Event UUID")
     field(:url, :string, description: "The ActivityPub Event URL")
     field(:local, :boolean, description: "Whether the event is local or not")
diff --git a/lib/mobilizon_web/schema/events/participant.ex b/lib/mobilizon_web/schema/events/participant.ex
index f811299af..75f9c8954 100644
--- a/lib/mobilizon_web/schema/events/participant.ex
+++ b/lib/mobilizon_web/schema/events/participant.ex
@@ -5,18 +5,34 @@ defmodule MobilizonWeb.Schema.Events.ParticipantType do
   use Absinthe.Schema.Notation
   import Absinthe.Resolution.Helpers, only: [dataloader: 1]
   alias MobilizonWeb.Resolvers
+  alias Mobilizon.Events
+  alias Mobilizon.Actors
 
   @desc "Represents a participant to an event"
   object :participant do
-    field(:event, :event,
+    field(
+      :event,
+      :event,
       resolve: dataloader(Events),
       description: "The event which the actor participates in"
     )
 
-    field(:actor, :actor, description: "The actor that participates to the event")
+    field(
+      :actor,
+      :actor,
+      resolve: dataloader(Actors),
+      description: "The actor that participates to the event"
+    )
+
     field(:role, :integer, description: "The role of this actor at this event")
   end
 
+  @desc "Represents a deleted participant"
+  object :deleted_participant do
+    field(:event, :deleted_object)
+    field(:actor, :deleted_object)
+  end
+
   object :participant_queries do
     @desc "Get all participants for an event uuid"
     field :participants, list_of(:participant) do
@@ -26,4 +42,22 @@ defmodule MobilizonWeb.Schema.Events.ParticipantType do
       resolve(&Resolvers.Event.list_participants_for_event/3)
     end
   end
+
+  object :participant_mutations do
+    @desc "Join an event"
+    field :join_event, :participant do
+      arg(:event_id, non_null(:integer))
+      arg(:actor_id, non_null(:integer))
+
+      resolve(&Resolvers.Event.actor_join_event/3)
+    end
+
+    @desc "Leave an event"
+    field :leave_event, :deleted_participant do
+      arg(:event_id, non_null(:integer))
+      arg(:actor_id, non_null(:integer))
+
+      resolve(&Resolvers.Event.actor_leave_event/3)
+    end
+  end
 end
diff --git a/test/mobilizon_web/resolvers/event_resolver_test.exs b/test/mobilizon_web/resolvers/event_resolver_test.exs
index 01a775fee..2c1ee0b08 100644
--- a/test/mobilizon_web/resolvers/event_resolver_test.exs
+++ b/test/mobilizon_web/resolvers/event_resolver_test.exs
@@ -60,63 +60,6 @@ defmodule MobilizonWeb.Resolvers.EventResolverTest do
                json_response(res, 200)["errors"]
     end
 
-    test "list_participants_for_event/3 returns participants for an event", context do
-      # Plain event
-      category = insert(:category)
-
-      event =
-        @event
-        |> Map.put(:organizer_actor_id, context.actor.id)
-        |> Map.put(:category_id, category.id)
-
-      {:ok, event} = Events.create_event(event)
-
-      query = """
-      {
-        participants(uuid: "#{event.uuid}") {
-          role,
-          actor {
-              preferredUsername
-          }
-        }
-      }
-      """
-
-      res =
-        context.conn
-        |> get("/api", AbsintheHelpers.query_skeleton(query, "participants"))
-
-      assert json_response(res, 200)["data"]["participants"] == [
-               %{
-                 "actor" => %{"preferredUsername" => context.actor.preferred_username},
-                 "role" => "creator"
-               }
-             ]
-
-      # Adding two participants
-      actor2 = insert(:actor)
-      actor3 = insert(:actor)
-      # This one won't get listed (as not approved)
-      participant = insert(:participant, event: event, actor: actor2, role: :not_approved)
-      # This one will (as a participant)
-      participant2 = insert(:participant, event: event, actor: actor3, role: :participant)
-
-      res =
-        context.conn
-        |> get("/api", AbsintheHelpers.query_skeleton(query, "participants"))
-
-      assert json_response(res, 200)["data"]["participants"] == [
-               %{
-                 "actor" => %{"preferredUsername" => context.actor.preferred_username},
-                 "role" => "creator"
-               },
-               %{
-                 "actor" => %{"preferredUsername" => participant2.actor.preferred_username},
-                 "role" => "participant"
-               }
-             ]
-    end
-
     test "create_event/3 creates an event", %{conn: conn, actor: actor, user: user} do
       category = insert(:category)
 
diff --git a/test/mobilizon_web/resolvers/participant_resolver_test.exs b/test/mobilizon_web/resolvers/participant_resolver_test.exs
new file mode 100644
index 000000000..ca5d0ddab
--- /dev/null
+++ b/test/mobilizon_web/resolvers/participant_resolver_test.exs
@@ -0,0 +1,372 @@
+defmodule MobilizonWeb.Resolvers.ParticipantResolverTest do
+  use MobilizonWeb.ConnCase
+  alias Mobilizon.Events
+  alias MobilizonWeb.AbsintheHelpers
+  import Mobilizon.Factory
+
+  @event %{
+    description: "some body",
+    title: "some title",
+    begins_on: Ecto.DateTime.utc(),
+    uuid: "b5126423-f1af-43e4-a923-002a03003ba4",
+    url: "some url"
+  }
+
+  setup %{conn: conn} do
+    user = insert(:user)
+    actor = insert(:actor, user: user, preferred_username: "test")
+
+    {:ok, conn: conn, actor: actor, user: user}
+  end
+
+  describe "Participant Resolver" do
+    test "actor_join_event/3 should create a participant", %{conn: conn, user: user, actor: actor} do
+      event = insert(:event)
+
+      mutation = """
+          mutation {
+            joinEvent(
+              actor_id: #{actor.id},
+              event_id: #{event.id}
+            ) {
+                role,
+                actor {
+                  id
+                },
+                event {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert json_response(res, 200)["errors"] == nil
+      assert json_response(res, 200)["data"]["joinEvent"]["role"] == "participant"
+      assert json_response(res, 200)["data"]["joinEvent"]["event"]["id"] == event.id
+      assert json_response(res, 200)["data"]["joinEvent"]["actor"]["id"] == actor.id
+
+      mutation = """
+         mutation {
+            joinEvent(
+              actor_id: #{actor.id},
+              event_id: #{event.id}
+            ) {
+                role
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "already a participant"
+    end
+
+    test "actor_join_event/3 should check the actor is owned by the user", %{
+      conn: conn,
+      user: user
+    } do
+      event = insert(:event)
+
+      mutation = """
+          mutation {
+            joinEvent(
+              actor_id: 1042,
+              event_id: #{event.id}
+            ) {
+                role
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "not owned"
+    end
+
+    test "actor_join_event/3 should check the event exists", %{
+      conn: conn,
+      user: user,
+      actor: actor
+    } do
+      mutation = """
+          mutation {
+            joinEvent(
+              actor_id: #{actor.id},
+              event_id: 1042
+            ) {
+                role
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "Event id not found"
+    end
+
+    test "actor_leave_event/3 should delete a participant from an event", %{
+      conn: conn,
+      user: user,
+      actor: actor
+    } do
+      event = insert(:event, %{organizer_actor: actor})
+      participant = insert(:participant, %{actor: actor, event: event})
+      participant2 = insert(:participant, %{event: event})
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: #{event.id}
+            ) {
+                actor {
+                  id
+                },
+                event {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert json_response(res, 200)["errors"] == nil
+      assert json_response(res, 200)["data"]["leaveEvent"]["event"]["id"] == event.id
+      assert json_response(res, 200)["data"]["leaveEvent"]["actor"]["id"] == participant.actor.id
+
+      query = """
+      {
+        participants(uuid: "#{event.uuid}") {
+          role,
+          actor {
+              preferredUsername
+          }
+        }
+      }
+      """
+
+      res =
+        conn
+        |> get("/api", AbsintheHelpers.query_skeleton(query, "participants"))
+
+      assert json_response(res, 200)["data"]["participants"] == [
+               %{
+                 "actor" => %{"preferredUsername" => participant2.actor.preferred_username},
+                 "role" => "creator"
+               }
+             ]
+    end
+
+    test "actor_leave_event/3 should check if the participant is the only creator", %{
+      conn: conn,
+      actor: actor,
+      user: user
+    } do
+      participant = insert(:participant, %{actor: actor})
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: #{participant.event.id}
+            ) {
+                actor {
+                  id
+                },
+                event {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] ==
+               "You can't leave event because you're the only event creator participant"
+
+      # If we have a second participant but not an event creator
+      insert(:participant, %{event: participant.event, role: :participant})
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: #{participant.event.id}
+            ) {
+                actor {
+                  id
+                },
+                event {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] ==
+               "You can't leave event because you're the only event creator participant"
+    end
+
+    test "actor_leave_event/3 should check the user is logged in", %{conn: conn, actor: actor} do
+      participant = insert(:participant, %{actor: actor})
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: #{participant.event.id}
+            ) {
+                actor {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "logged-in"
+    end
+
+    test "actor_leave_event/3 should check the actor is owned by the user", %{
+      conn: conn,
+      user: user
+    } do
+      participant = insert(:participant)
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: #{participant.event.id}
+            ) {
+                actor {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "not owned"
+    end
+
+    test "actor_leave_event/3 should check the participant exists", %{
+      conn: conn,
+      user: user,
+      actor: actor
+    } do
+      participant = insert(:participant, %{actor: actor})
+
+      mutation = """
+          mutation {
+            leaveEvent(
+              actor_id: #{participant.actor.id},
+              event_id: 1042
+            ) {
+                actor {
+                  id
+                }
+              }
+            }
+      """
+
+      res =
+        conn
+        |> auth_conn(user)
+        |> post("/api", AbsintheHelpers.mutation_skeleton(mutation))
+
+      assert hd(json_response(res, 200)["errors"])["message"] =~ "Participant not found"
+    end
+
+    test "list_participants_for_event/3 returns participants for an event", context do
+      # Plain event
+      category = insert(:category)
+
+      event =
+        @event
+        |> Map.put(:organizer_actor_id, context.actor.id)
+        |> Map.put(:category_id, category.id)
+
+      {:ok, event} = Events.create_event(event)
+
+      query = """
+      {
+        participants(uuid: "#{event.uuid}") {
+          role,
+          actor {
+              preferredUsername
+          }
+        }
+      }
+      """
+
+      res =
+        context.conn
+        |> get("/api", AbsintheHelpers.query_skeleton(query, "participants"))
+
+      assert json_response(res, 200)["data"]["participants"] == [
+               %{
+                 "actor" => %{"preferredUsername" => context.actor.preferred_username},
+                 "role" => "creator"
+               }
+             ]
+
+      # Adding two participants
+      actor2 = insert(:actor)
+      actor3 = insert(:actor)
+      # This one won't get listed (as not approved)
+      insert(:participant, event: event, actor: actor2, role: :not_approved)
+      # This one will (as a participant)
+      participant2 = insert(:participant, event: event, actor: actor3, role: :participant)
+
+      res =
+        context.conn
+        |> get("/api", AbsintheHelpers.query_skeleton(query, "participants"))
+
+      assert json_response(res, 200)["data"]["participants"] == [
+               %{
+                 "actor" => %{"preferredUsername" => context.actor.preferred_username},
+                 "role" => "creator"
+               },
+               %{
+                 "actor" => %{"preferredUsername" => participant2.actor.preferred_username},
+                 "role" => "participant"
+               }
+             ]
+    end
+  end
+end