public function addGroup(Request $request)
 {
     $user_id = $request->get('id');
     $group_id = $request->get('group_id');
     try {
         $this->user_repository->addGroup($user_id, $group_id);
     } catch (JacopoExceptionsInterface $e) {
         return Redirect::route('users.edit', ["id" => $user_id])->withErrors(new MessageBag(["name" => Config::get('acl_messages.flash.error.user_group_not_found')]));
     }
     return Redirect::route('users.edit', ["id" => $user_id])->withMessage(Config::get('acl_messages.flash.success.user_group_add_success'));
 }