SCRUM#282: fixing return role_ids from users

app/serializers/user_serializer.rb

@@ -36,6 +36,10 @@ class UserSerializer < ActiveModel::Serializer
     object.learning_objects.where('state = ?', LearningObject.states[:published]).count
   end
 
+  def role_ids
+    object.roles.all.ids
+  end
+
   attributes \
       :id,
       :email,