Allow to join an open group

Also:

* Refactor interacting with a remote event so that you can interact with
  a remote group as well
* Add a setting for group admins to pick between an open and invite-only
  group
* Fix new groups without posts/todos/resources/events/conversations URL
  set
* Repair local groups that haven't got their
  posts/todos/resources/events/conversations URL set
* Add a scheduled job to refresh remote groups every hour
* Add a user setting to pick when to receive notifications when there's
  new members to approve (will be used when this feature is available)
* Fix pagination for members

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/graphql/api/search.ex

@@ -72,6 +72,18 @@ defmodule Mobilizon.GraphQL.API.Search do
     end
   end
 
+  def interact(uri) do
+    case ActivityPub.fetch_object_from_url(uri) do
+      {:ok, object} ->
+        {:ok, object}
+
+      {:error, _err} ->
+        Logger.debug(fn -> "Unable to find or make object from URI '#{uri}'" end)
+
+        {:error, :not_found}
+    end
+  end
+
   # If the search string is an username
   @spec process_from_username(String.t()) :: Page.t()
   defp process_from_username(search) do