title: Spring Security 5.2.1 OAuth2 with XING not working
body: <p>I have set up OAuth2 with Spring Security for my localhost test application with</p>
  
  <ul>
  <li>Azure</li>
  <li>Facebook</li>
  <li>GitHub</li>
  <li>Google</li>
  </ul>
  
  <p>Now I tried to do the same with Xing <a href="https://dev.xing.com/docs/authentication" rel="nofollow noreferrer">https://dev.xing.com/docs/authentication</a> (OAuth2).</p>
  
  <pre><code>spring:
    security:
      oauth2:
        client:
          provider:
            xing:
              authorization-uri: https://api.xing.com/auth/oauth2/authorize
              token-uri: https://api.xing.com/auth/oauth2/token
          registration:
            xing:
              client-id: ${XING_CLIENT_ID}
              client-secret: ${XING_CLIENT_SECRET}
              client-name: Xing
              redirect-uri: '{baseUrl}/login/oauth2/code/{registrationId}'
              authorization-grant-type: authorization_code
  </code></pre>
  
  <p>Looks similar to the Facebook configuration.</p>
  
  <p>After the login in the 4 step from the XING Documentation an error is thrown: <code>[invalid_client] Invalid client id and/or client secret.</code></p>
  
  <p>Using debugger I found out, that client id and secret are not added to that Authorization Request, not even when requesting GitHub. Now I wonder because I thought this is essential in this step.</p>
  
  <p>DefaultAuthorizationCodeTokenResponseClient.java Line 75:</p>
  
  <p><a href="https://i.stack.imgur.com/XyjUA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XyjUA.png" alt="Request to GitHub"></a></p>
  
  <p><a href="https://i.stack.imgur.com/nIDrR.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nIDrR.png" alt="Request to Xing"></a></p>
  
  <p>In my understanding, Client ID and Secret would have to be used for all OAuth2 providers at this point, right?</p>
  
  <p>Regardless, do I need to override the DefaultAuthorizationCodeTokenResponseClient class somehow, or is there an easy way to implement a solution for XING here?</p>