Revisit CAS documentation

[marcusdacoregio]

The CAS documentation is lacking Java Configuration examples and should be revisited since the support is being added back with #11674

[marcusdacoregio]

This project has the basic configuration https://github.com/marcusdacoregio/spring-security-6-cas and can be used as a reference

[hdeadman]

This project has the basic configuration https://github.com/marcusdacoregio/spring-security-6-cas and can be used as a reference

I wish I would have seen that comment before I worked on a PR to add a CAS sample to the spring-security-samples project. I did some documentation updates locally based the stuff I added to the samples project but not sure how to submit them as their own PR until the CAS changes are merged. I will take a look at your sample tomorrow.