title: LUIS pattern feature does not detect my entity
body: <p>I want to detect an entity from an intent, that might be written in several ways:</p>
  
  <p>AB 123456<br>
  AB 123 456<br>
  AB123456  </p>
  
  <p>AB is an option from a closed list, and the rest should be detected as number(s). As long as there <strong>is a space between AB and the number</strong>, the list item and the number(s) are detected/resolved.   </p>
  
  <p>I discovered the pattern feature and hoped this could help out the parser.</p>
  
  <p>Unfortunately, the entity can still not be recognized. I tried to write the pattern in different ways, with no success.</p>
  
  <p>^([A-Za-z]{1,2})([0-9 ]+)$  </p>
  
  <p>([a-z]{2})([\d ]+)  </p>
  
  <p>[a-z]{2}[\d ]+</p>
  
  <p>Any idea?</p>