Add ability to delete a group

lib/mobilizon/actors/user.ex

@@ -144,4 +144,16 @@ defmodule Mobilizon.Actors.User do
   def is_confirmed(%User{} = user) do
     {:ok, user}
   end
+
+  def owns_actor(%User{default_actor_id: default_actor_id} = user, %Actor{id: actor_id})
+      when default_actor_id == actor_id do
+    {:is_owned, true}
+  end
+
+  def owns_actor(%User{actors: actors} = user, actor_id) do
+    case Enum.any?(actors, fn a -> a.id == actor_id end) do
+      true -> {:is_owned, true}
+      _ -> {:is_owned, false}
+    end
+  end
 end