Log group creation and removal

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/group.rb

@@ -101,10 +101,14 @@ class Group < Namespace
   end
   def post_create_hook
+    Gitlab::AppLogger.info("Group \"#{name}\" was created")
+
     system_hook_service.execute_hooks_for(self, :create)
   end
   def post_destroy_hook
+    Gitlab::AppLogger.info("Group \"#{name}\" was removed")
+
     system_hook_service.execute_hooks_for(self, :destroy)
   end