Idea: add OAUTH2 support

[unquietwiki]

Not sure how feasible this is, but a lot of web-based systems are using OAUTH2 instead of CAS/Shibboleth/LDAP for authentication these days. What would be interesting would be to be able to attach support to CASino such that it could remain a single authentication provider, but be able to either Facebook/Google/Twitter/etc as source credentials for CAS; or use the existing LDAP/database mechanisms to provide OAUTH2 authorization to servers that need it.

There's at least one Ruby library out there that appears to have a similar MIT license, that could be a starting point. https://github.com/nov/rack-oauth2