protected function registerUserProvider()
    {
        $this->app['lockdown.user'] = $this->app->share(
            function ($app) {
                $userModel = config('lockdown.user');
                return new UserProvider($userModel);
            }
        );
        
        $this->app['auth']->provider(
            'lockdown',
            function ($app) {
                return $app['lockdown.user'];
            }
        );
    }