IdPv3 CAS Protocol Update

[Marvin Addison]

I've done enough work to share:

https://github.com/serac/shibboleth-idp-ext-cas

Only the ticket request portion of the CAS protocol is implemented,
but it's enough to get a feel for how integration would look and
initial signs are promising. The biggest obstacle at present is
determining how to interact with the Shib authentication flow. I
imagine it will be a subflow call, and I've modeled as such, but the
details are unclear. I not only need to call the flow but pass context
parameters that indicate forced authentication is required under some
conditions. Any suggestions or recommendations for interacting with
the authn flow?

Next step is CAS 2.0 protocol ticket validation, which should be
straightforward.

M