title: How to access token additionalInformation to validate expression-based access control
body: <p>I succesfully added <code>user_id</code> additionnal information on the generated tokens on the authorization server side by implementing a <code>TokenEnhancer</code>. Here is a token generated:</p>
  
  <p><code>
  {"access_token":"ccae1713-00d4-49c2-adbf-e699c525d53e","token_type":"bearer","expires_in":31512,"scope":"end-user","user_id":2}
  </code></p>
  
  <p>Now, on the Resource server side, which is a completely separate spring project communicating through a <code>RemoteTokenServices</code>, i would like to use theses informations with method <code>expression-based access control</code>. For example i would like to use the added <code>user_id</code> data (it is Spring Data JPA repository for use with Spring Data Rest):</p>
  
  <p><code>
  @PreAuthorize("#oauth2.hasScope('admin') or #id == authentication.principal.user_id")
  @Override
  UserAccount findOne (@P("id") Integer id);
  </code></p>
  
  <p>The <code>#oauth2.hasScope('admin')</code> works as expected but the <code>#id == authentication.principal.user_id"</code> part obviously not.</p>
  
  <p>how can i access to the additional data added to the token on expression-based access control ?</p>