title: JSON request to create entity with existent inner object
body: <p>I develop rest api and think about following task. I need to post a vehicle entity and bind existing driver to it. What is the common approach to format json for such request?
  I choose one of these variants, but maybe there are better solutions: </p>
  
  <pre><code>1. {"model":"Corolla","number":"12345", "driver": {"id": 5}}
  
  2. {"model":"Corolla","number":"12345", "driver": {"id": 5, "name": "John"}}
  
  3. {"model":"Corolla","number":"12345", "driverId": 5} 
  </code></pre>
  
  <p>The question is about how to pass information about already created driver entity with known id.</p>