Document SAML IDP related instructions for setting up an SSO

Since we removed the SAML IDP related instructions from the rc/cod-heat-stack repo (refer https://code.rc.uab.edu/rc/cod-heat-stack/-/issues/17) because the applications like OOD are deployed using CICD in rc/hpc-factory. It makes sense to document it in the rc/hpc-factory repo, where the applications needing SSO could benefit from these SAML IDP config instructions.

Note that the SAML IDP (samltest.id) that we used before as a test target is no longer in service.

As an immediate fix, put a placeholder comment to let the users know that we are working on setting up the alternative to samltest.id

When ready, update the instructions to use an alternative to samltest.id like mocksaml.com --https://github.com/ory/mocksaml (refer # #295)