title: write regex in JsonFormat pattern
body: <pre><code>@JsonFormat(shape = JsonFormat.Shape.STRING, pattern ="yyyy-MM-dd'T'HH:mm:ss.SSS")
  </code></pre>
  
  <p>is it possible to write regex in pattern? I could not </p>
  
  <p>pattern ="yyyy-MM-dd'T'HH:mm:ss.SSS(Z?)"</p>
  
  <p>I want to make Z as optional</p>
  
  <p>any links suggestions?</p>