This PR replaces Framework's Base64Utils with JDK's Base64 as it has been deprecated in https://github.com/spring-projects/spring-framework/pull/28434.
Comment From: mhalbritter
Categorized as task, as this has no visible effect on Boot users.
Comment From: wilkinsona
We should do this in 3.0.x as our build will fail due to the deprecation warnings when we switch to Framework 6.0.5 snapshots.
Comment From: mhalbritter
Thank you!