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/federation/activity_stream/converter/member.ex

@@ -20,7 +20,7 @@ defmodule Mobilizon.Federation.ActivityStream.Converter.Member do
   end
 
   @doc """
-  Convert an event struct to an ActivityStream representation.
+  Convert an member struct to an ActivityStream representation.
   """
   @spec model_to_as(MemberModel.t()) :: map
   def model_to_as(%MemberModel{} = member) do