public static function getAllowedExtensions()
    {
        $config = static::config()->get('allowed_extensions');

        $allowedExtensions = [];
        foreach ($config as $key => $value) {
            if (is_int($key)) {
                // Numeric indexes, example: [jpg, png, gif]
                $key = $value;
                $value = true;
            }

            // Skip disabled extensions
            if (in_array($value, [null, false], true)) {
                continue;
            }

            $allowedExtensions[] = strtolower($key);
        }
        return $allowedExtensions;
    }