store info about all users

[EarthenSky]

Store info about whether a user has authenticated with the sfu api before, what kind of user they are (student, professor, etc.), if they're a member of the CSSS or not, etc..

This should use the CAS API, & will require reading it & figuring out what information we can get about a user. We should also decide what to do if a user's kind changes (ie. student -> alumni).