public static function shipped($orderId, $shippedAt = 0)
    {
        $url = static::classUrl();
        $url = $url . '/' . $orderId . '/shipped';
        list($ret, $code) = parent::staticRequest('post', $url, [
            'shippedAt' => date('c', $shippedAt ? $shippedAt : time()),
        ]);

        return (object)[
            'code' => $code,
            'status' => $code === 204? 'success' : 'failed'
        ];
    }