title: Can't find some deprecated constant variables in spring security
body: <p>I'm <strong><code>upgrading spring security</code></strong> from <code>2.0.5</code> to <code>4.2.0</code>, I know its quite a big upgrade, But I have to do that. All configuration errors are resolved, but Now having some errors in some java codes. I have already solved some of it.
  The errors I'm having now is like my project is using some Constants from class <br> <code>AuthenticationProcessingFilter</code>, those are<br> <code>SPRING_SECURITY_SAVED_REQUEST_KEY</code>,<br> <code>SPRING_SECURITY_LAST_USERNAME_KEY</code> and <br><code>SPRING_SECURITY_LAST_EXCEPTION_KEY</code> , <br>here I've solved the problem with <code>SPRING_SECURITY_LAST_EXCEPTION_KEY</code> <br>as I used <code>WebAttributes.AUTHENTICATION_EXCEPTION</code>, But can't find any alternatives for rest two. Can anyone help me with this ?</p>