feat : order rest api 在最顶层添加图片url的第二种方法

app/code/Magento/Sales/Api/Data/OrderItemInterface.php

@@ -23,6 +23,10 @@ interface OrderItemInterface extends \Magento\Framework\Api\ExtensibleDataInterf
      * Item ID.
      */
     const ITEM_ID = 'item_id';
+
+
+    const IMAGE   = 'image';
+
     /*
      * Order ID.
      */
@@ -1824,4 +1828,9 @@ interface OrderItemInterface extends \Magento\Framework\Api\ExtensibleDataInterf
      * @return $this
      */
     public function setExtensionAttributes(\Magento\Sales\Api\Data\OrderItemExtensionInterface $extensionAttributes);
+
+    /**
+     * @return string|null
+     */
+    public function getImage();
 }

app/code/Magento/Sales/Model/Order/Item.php

@@ -2415,4 +2415,18 @@ class Item extends AbstractModel implements OrderItemInterface
     {
         return $this->getQtyToShip() > $this->getQtyToCancel();
     }
+
+    /**
+     * @inheritdoc
+     */
+    public function getImage() {
+        $product = $this->productRepository->get($this->getSku());
+        if ($product) {
+            $objectManager = \Magento\Framework\App\ObjectManager::getInstance();
+            $storeManager = $objectManager->get('\Magento\Store\Model\StoreManagerInterface');
+            $hostname = $storeManager->getStore()->getBaseUrl();
+            return $hostname."media/catalog/product/".$product->getData('thumbnail');
+        }
+        return "null";
+    }
 }