title: How to return custom message if Authorize fails in WebAPI
body: <p>In my WebAPI project, I have number of apis which are decorated with <code>[Authorize]</code> attribute. </p>
  
  <pre><code>[Authorize]
  public HttpResponseMessage GetCustomers()
  {
     //my api
  }
  </code></pre>
  
  <p>In case user doesn't have the right token, an access denied exception is returned to the user. </p>
  
  <p>But what I need is that in any such case, I need to return the custom response message as. </p>
  
  <pre><code>{
    "StatusCode" : 403,
    "message": "You donot have sufficient permission"
  }
  </code></pre>
  
  <p>How do I return this custom message in case authorization fails.</p>
  
  <p>Please note: </p>
  
  <ul>
  <li><em>I am using Owin - Token based authentication.</em></li>
  <li><em>I am <strong>not</strong> storing the access token in my database or anywhere else.</em></li>
  </ul>