public static function addBuilder($appId, $builderFunction)
    {
        if (array_key_exists($appId, static::$builders)) {
            throw new Exception\FacadeException("Builder with {$appId} already exists!");
        }

        if (!is_callable($builderFunction)) {
            throw new Exception\FacadeException("Builder function for {$appId} is not callable!");
        }

        static::$builders[$appId] = $builderFunction;

        return true;
    }