Add CAS as provider

[hdeadman]

Signed-off-by: Hal Deadman [email protected]

When I pointed this app at my strapi 3.2.3 app with CAS provider in an extension layer and configured to point at my dev lab CAS server configured with OIDC support and a service definition that allows logins from service running at http://localhost:1337, I was able click Connect to cas button got redirected to CAS and got JWT token seen in screen shot.