Update What's New for 6.3

Author: sjohnr

docs/modules/ROOT/pages/whats-new.adoc

@@ -19,3 +19,14 @@ Below are the highlights of the release.
 == Crypto
 
 - https://github.com/spring-projects/spring-security/issues/14202[gh-14202] - Migrated spring-security-rsa into spring-security-crypto
+
+== OAuth2
+
+- https://github.com/spring-projects/spring-security/issues/13259[gh-13259] - Customize when UserInfo is called
+- https://github.com/spring-projects/spring-security/pull/14168[gh-14168] - Introduce Customizable AuthorizationFailureHandler in OAuth2AuthorizationRequestRedirectFilter
+- https://github.com/spring-projects/spring-security/issues/5199[gh-5199], https://github.com/spring-projects/spring-security/issues/14701[gh-14701] - Add support for OAuth 2.0 Token Exchange Grant
+- https://github.com/spring-projects/spring-security/issues/14672[gh-14672] - Customize mapping the OidcUser from OidcUserRequest and OidcUserInfo
+
+== Documentation
+
+- https://github.com/spring-projects/spring-security/pull/14263[gh-14263] - xref:servlet/authentication/passwords/caching.adoc[(docs)] - Add documentation for CachingUserDetailsService