Conform better to the CAS protocol specification
Conform better to the CAS protocol specification

Redirect to CAS's /login endpoint properly, and
don't require an <attributes> element.

Signed-off-by: Shell Turner <a1791743fd5f6f3c6a5916c490f2f0fa3c722118@gmail.com>

TribeMedia/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse