Using a different LDAP attribute for the principal ID for Google Apps SAML only?

[Brodie Rao]

I'm using CAS server 3.2.1 with an LDAP server and I'd like to have it 
use a different attribute for finding the principal ID for Google Apps 
SAML requests. Is it possible to configure the CAS server to send a 
different principal ID for SAML requests? More specifically, I want it 
to return the mailNickname LDAP attribute for Google Apps, and 
sAMAccountName for any other request (which is the attribute queried on 
by the LDAP authentication handler).

If that's not possible, is it possible to configure a second instance of 
the CAS server mounted at a different URL that shares the same ticket 
store as the first server? That way I could point Google Apps to that 
second instance, and keep existing applications pointed at the first 
instance.