title: Rails run after create on parent model after saving parent model AND nested associations
body: <p>I am creating a new resource in my Rails app, the JSON sent to my endpoint looks like this:</p>
  
  <pre><code>{
    "resource1": {
      "resource2_attributes": [{
        "name": "Test 1",
        "resource3_attributes": [{
          "field1": "test"
        }]
      }]
    }
  }
  </code></pre>
  
  <p>The nested attributes are working correctly, and the associations on the parent model are being set.</p>
  
  <p>However, when <code>resource1</code> at the top level is saved, the <code>after_create</code> callback on the model is triggered (prior to saving the associations).  The <code>after_create</code> callback on <code>Resource1</code> uses the child associations for its logic.</p>
  
  <p>How can I make my Rails app save the parent model along with the child associations, <em>and then</em> run the callback?</p>