title: Custom ApiExplorer with Namespace based ApiControllers
body: <p>I'm trying to add API documentation at my backend system.
  Default ApiExplorer and Help page worked absolutely great until the moment I introduced versions to my Api Controllers.</p>
  
  <p>In order to add versions I created sub folders under the Controllers folder:</p>
  
  <ul>
  <li>v1 </li>
  <li>v2</li>
  <li>v3</li>
  </ul>
  
  <p>and have version based Api Controllers there. In order to have my Api discoverable I have to rewrite DefaultHttpControllerSelector to take into account namespaces provided by any client and map them to right controllers:</p>
  
  <ul>
  <li><a href="http://backend.com/api/v1/controller/action" rel="noreferrer">http://backend.com/api/v1/controller/action</a></li>
  <li><a href="http://backend.com/api/v2/controller/action" rel="noreferrer">http://backend.com/api/v2/controller/action</a></li>
  </ul>
  
  <p>This have broken my default ApiExplorer and the following property returns ZERO api descriptions</p>
  
  <pre><code>Configuration.Services.GetApiExplorer().ApiDescriptions
  </code></pre>
  
  <p>How can I customize existent ApiExplorer and help him to find my Api Controllers and not to rewrite whole ApiExplorer implementation. I really need just to show where to find my Api Controllers.</p>
  
  <p>Please advise.</p>