title: jackson make two json attributes of one java attribute
body: <p>I have a little bit of a comfort problem using jackson in a rest api.
  I am using jackson to serialize object that have attributes of any type in java.time like:</p>
  
  <pre><code>public class DomainObject{
     public LocalDateTime start;
  }
  </code></pre>
  
  <p>I can use jackson to produce something like this:</p>
  
  <pre><code>{
      start: '2017-12-31 17:35:22'
  }
  </code></pre>
  
  <p>And i can use it to produce something like this:</p>
  
  <pre><code>{
      start: 102394580192345 //milliseconds
  }
  </code></pre>
  
  <p>But i would like to have both, the milliseconds to workwith in JS and the String representation for Users who use the rest-api purely without js-frontend. (Mostly me, for debugging)</p>
  
  <p>So is there any way, to make jackson produce the following?</p>
  
  <pre><code>{
      start: 102394580192345 //milliseconds
      startString: '2017-12-31 17:35:22'
  }
  </code></pre>