Fixes an issue where auto-configuration for Spring Authorization Server
was overriding the default exception handling (AuthenticationEntryPoint)
resulting in anonymous requests to the token endpoint being redirected
to the Spring Security login page instead of returning 401 Unauthorized.
Auto-configuration now registers a defaultAuthenticationEntryPointFor
that is added to any other entry points already configured.
See gh-35368
Phillip Webb
Brian Clozel
Moritz Halbritter
Steve Riesenberg
Andy Wilkinson
Madhura Bhave