title: Ember-data Serialize/Deserialize embedded records on 3rd level
body: <p>Pardon me for coming up with this title but I really don't know how to ask this so I'll just explain.
  Model: Group (has) User (has) Post
  Defined as:</p>
  
  <pre><code>// models/group.js
  name: DS.attr('string'),
  
  // models/user.js
  name: DS.attr('string'),
  group: DS.belongsTo('group')
  
  // models/post.js
  name: DS.attr('string'),
  user: DS.belongsTo('user'),
  </code></pre>
  
  <p>When I request <code>/posts</code>, my server returns this embedded record:</p>
  
  <pre><code>{
    "posts": [
      {
        "id": 1,
        "name": "Whitey",
        "user": {
          "id": 1,
          "name": "User 1",
          "group": 2
        }
      }
    ]
  }
  </code></pre>
  
  <p>Notice that the <code>group</code> didn't have the group record but an id instead.</p>
  
  <p>With my serializers:</p>
  
  <pre><code>// serializers/user.js
  export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
      attrs: {
          group: {embedded: 'always'}
      }
  });
  
  // serializers/post.js
  export default DS.RESTSerializer.extend(DS.EmbeddedRecordsMixin, {
      attrs: {
          user: {embedded: 'always'}
      }
  });
  </code></pre>
  
  <p>This expects that the <code>User</code> and <code>Post</code> model have embedded records in them. However, it entails a problem since in the json response doesn't have an embedded <code>group</code> record.</p>
  
  <h3>The question is, is there a way I can disable embedding records in the 3rd level?</h3>
  
  <p>Please help.</p>