public static function register($registerViewExtension = false, Recaptcha $recaptcha = null, $appName = null)
    {
        $app = call_user_func_array(['\Slim\Slim', 'getInstance'], array_filter([$appName]));

        $recaptcha = self::registerSingleton($app, $recaptcha);

        if ($registerViewExtension) {
            self::registerViewExtension($app, $recaptcha);
        }
    }