Refresh Keycloak docs in BigBang repo

A Big Bang end user reported that some Keycloak documentation is out-of-date. It's a good time to review the following docs and correct any info that is no longer accurate.

Use big bang repo keycloak docs for setting up an SSO integration. Update anything that's out of date or no longer accurate.

Docs include

• sso quickstart
• understanding bigbang package architecture for keycloak
• confirm if protect=keycloak is still a valid label as described in benefits of using bigbang (Moved to #2233 (closed) )