protected function registerGroupRepository()
    {
        $this->app->singleton('grouprepository', function ($app) {
            $model = $app['config']['sentry.groups.model'];
            $group = new $model();

            $validator = $app['validator'];

            return new GroupRepository($group, $validator);
        });

        $this->app->alias('grouprepository', GroupRepository::class);
    }