I really wouldn't advise to use CAS in 2020. It's an historical curiosity that stopped being relevant some years ago. It's an old protocol to do single sign on

I really wouldn't advise to use CAS in 2020. It's an historical curiosity that stopped being relevant some years ago. It's an old protocol to do single sign on within a company. It worked well and I've seen it used in large companies circa 2010, allowing to support sso in their internal web applications, for employees. CAS is irrelevant now. The world has standardized on OpenID Connect (and SAML as second choice). Anything that's on CAS was migrated or is pending migration to OIDC. As a developer you will have to deal with OIDC (and maybe SAML) for integrations with google auth, facebook auth, microsoft active directory. You really don't want to go for a dying ecosystem (CAS), that's a dead end for your career.