Implement "Login with Google" auth feature

Created by: deepakduggirala

@charlesbrandt

• How to differentiate between accounts of the same user logged via IU vs google. keep as separate accounts / merge them? Currently, only one email can be stored per account, how to handle multiple (@gmail and @iu.edu) emails while also ensuring uniqueness?
• Login vs Signup: Allow new users to create accounts? or an operator / admin should create the account and only then they can log in?

Add auth_mode to user table in UI which show the mode (google, IU) of the last successful login.