title: Has support Doctrine Sluggable Unique_base option multiple fields?
body: <p>I have a post table like as </p>
  
  <pre><code>id  slug title  content  objectKey  objectId
  </code></pre>
  
  <p>I want generate slugs unique by 3 field. <code>[ title, objectKey, objectId ]</code></p>
  
  <p>How could make it ?</p>