Write comments on resource model Java classes

[saw303]

In the JSON spec file a field contains an attribute called x-comment.

{
      "name": "id",
      "type": "string",
      "x-comment": "my custom id"
}

The generator creates the following output.

public class MailGetResourceModel implements Serializable, ResourceModel, Identifiable<String> {
  // ...

  // The following Javadoc output should be generated
  /**
  * my custom id   
  */
  private String id;
  // ...
}