Merge branch 'fix-collection-next' into 'master'

Fix collection next attribute and add prev attribute

Closes #546

See merge request framasoft/mobilizon!785

lib/web/views/activity_pub/actor_view.ex

@@ -153,8 +153,18 @@ defmodule Mobilizon.Web.ActivityPub.ActorView do
       "orderedItems" => Enum.map(collection, &item/1)
     }
 
+    map =
       if offset < total do
         Map.put(map, "next", Actor.build_url(preferred_username, endpoint, page: page + 1))
+      else
+        map
+      end
+
+    map =
+      if offset > total do
+        Map.put(map, "prev", Actor.build_url(preferred_username, endpoint, page: page - 1))
+      else
+        map
       end
 
     map