Finish authentication system between frontend and backend

[tomdng]

Considerations

1. Do we want to stick with email/password login, Google sign-in, or both?
2. Do we also want to keep Admin and Students as separate tables? Because we could simplify this down into a User table that has an admin or student role and do things that way.

Implementation Details

• Use Auth0 or some other similar auth service so keep account creation/password update/forgot password features off of our hands
• I might still need to think about how the user maintains their login credentials so that they don't need to sign in every single time they open the app. Not sure how much work Auth0 is gonna take off of authentication.