title: Spring-data-rest jacksonHttpMessageConverter doesn't convert nested entity
body: <p>I am using spring-data-rest-webmvc:2.5.6.RELEASE. My application uses auto configuration to expose all endpoints simple I didn't provide any custom configuration. Consider the following domain classes</p>
  
  <p><strong>Order.java</strong></p>
  
  <pre><code>public class Order {
  
      @Id @GeneratedValue//
      private Long id;
      @ManyToOne(fetch = FetchType.LAZY)//
      private Person creator;
      private String type;
  
      public Order(Person creator) {
          this.creator = creator;
      }
  
      // getters and setters
  }
  </code></pre>
  
  <p><strong>Person.java</strong></p>
  
  <pre><code>pubic class Person {
  
      @Id @GeneratedValue private Long id;
  
      @Description("A person's first name") //
      private String firstName;
  
      @Description("A person's last name") //
      private String lastName;
  
      @Description("A person's siblings") //
      @ManyToMany //
      private List&lt;Person&gt; siblings = new ArrayList&lt;Person&gt;();
  
      @ManyToOne //
      private Person father;
  
      @Description("Timestamp this person object was created") //
      private Date created;
  
      @JsonIgnore //
      private int age;
  
      private int height, weight;
      private Gender gender;
  
      // ... getters and setters
  }
  </code></pre>
  
  <p>I am using a following curl command to POST a order</p>
  
  <pre><code>    curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' -d '{ \ 
     "creator": { \ 
       "firstName": "John", \ 
       "lastName": "Smith", \ 
       "age": 1 \ 
     }
   }' 'http://localhost:8080/orders'
  </code></pre>
  
  <p>The server throws 500 Internal Server Error. Because order.creator=null in hibernate insert query. But if I modify my curl request body as follows</p>
  
  <pre><code>curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' -d '{ \ "creator": "http://localhost:8080/creators/1" }' http://localhost:8080/orders'
  </code></pre>
  
  <p>the server returns 200 as expected. But I don't want to use the 2nd curl command, since my existing application requests with nested/expanded json entity in request body.</p>
  
  <p>Is there any configuration exists in spring-data-rest to make the 1st curl command successfull? or</p>
  
  <p>Is this an issue with spring-data-rest?</p>