title: How to add and retrieve metafields to order when adding new order via api
body: <p>I am trying to add metafields to new order as follows:</p>
  
  <pre><code>{       "order": {
      "line_items": [
        {
          "title": "Test Order item 1",
          "price": 0.00,
          "grams": "1700",
          "quantity": 1,      "taxable": false
        }
      ],
      "metafield": {
      "namespace": "inventory",
      "key": "amazonOrderId",
      "value": 123456789,
      "value_type": "integer"   },
      "email": "rahul@testOrder.com",
      "total_tax": 0.00   } }
  </code></pre>
  
  <p>The order is being created on shopify admin panel but on retrieving same order metafields are not returned. I am not sure where to find added metafield, is it added or not. Please help.
  Thanks</p>