missingOrderNumber example

        $cart = new Cart(Uuid::randomHex());
        $cart->setPrice($order->getPrice());
        $cart->setCustomerComment($order->getCustomerComment());
        $cart->setAffiliateCode($order->getAffiliateCode());
        $cart->setCampaignCode($order->getCampaignCode());
        $cart->setSource($order->getSource());
        $cart->addExtension(self::ORIGINAL_ID, new IdStruct($order->getId()));
        $orderNumber = $order->getOrderNumber();
        if ($orderNumber === null) {
            throw OrderException::missingOrderNumber($order->getId());
        }

        $cart->addExtension(self::ORIGINAL_ORDER_NUMBER, new IdStruct($orderNumber));
        /* NEXT-708 support: - transactions */

        $lineItems = LineItemTransformer::transformFlatToNested($order->getLineItems());

        $cart->addLineItems($lineItems);
        $cart->setDeliveries(