title: Django Rest Framework receive primary key value in POST and return model object as nested serializer
body: <p>I'm not completely sure that the title of my question is as specific as I wanted it to be, but this is the case:</p>
  
  <p>I have a <code>HyperlinkedModelSerializer</code> that looks like this:</p>
  
  <pre><code>class ParentArrivalSerializer(serializers.HyperlinkedModelSerializer):
      carpool = SchoolBuildingCarpoolSerializer()
  
      class Meta:
          model = ParentArrival
  </code></pre>
  
  <p>As you can see the <code>carpool</code> is defined as a nested serializer object and what I want is to be able to make a POST request to create a <code>ParentArrival</code> in this way (data as application/json):</p>
  
  <pre><code>{
      ...
      "carpool": "http://localhost:8000/api/school-building-carpools/10/"
      ...
  }
  </code></pre>
  
  <p>And receive the data in this way:</p>
  
  <pre><code>{
      "carpool": {
          "url": "http://localhost:8000/api/school-building-carpools/10/"
          "name": "Name of the carpool",
          ...
      }
  }
  </code></pre>
  
  <p>Basically, I'm looking for a way to deal with nested serializers without having to send data as an object (but id or url in this case) in POST request, but receiving the object as nested in the serialized response.</p>