title: How to accept JSON through Rails API without "_attributes" for nested fields
body: <p>I've written an API with Rails and need to accept some nested_attributes in API calls.</p>
  
  <p>Currently I send data via</p>
  
  <p><strong>PATCH /api/v1/vintages/1.json</strong></p>
  
  <pre><code>{
    "vintage": {
      "year": 2014,
      "name": "Some name",
      "foo": "bar",
      "sizes_attributes": [
        {
          "name": "large",
          "quantity": "12"
        },
        {
          "name": "medium",
          "quantity": "2"
        }
      ]
    }
  }
  </code></pre>
  
  <p>However, I'd like to perform the following:</p>
  
  <p><strong>PATCH /api/v1/vintages/1.json</strong></p>
  
  <pre><code>{
    "vintage": {
      "year": 2014,
      "name": "Some name",
      "foo": "bar",
      "sizes": [
        {
          "name": "large",
          "quantity": "12"
        },
        {
          "name": "medium",
          "quantity": "2"
        }
      ]
    }
  }
  </code></pre>
  
  <p>The difference being <strong>attributes</strong> being part of the key of the fields. I want to be able to <code>accept_nested_attributes_for :sizes</code> without having to use <code>_attributes</code> be a part of the JSON object.</p>
  
  <p>Anyone know how to manage this?</p>