Improve the student experience for signed in students

[mikenikles]

We have to de-couple the jwt token from being the gate-keeper to everything. At the moment, the jwt token set means it's a pre-order student and they get access to everything.

What we want instead: On the course landing page, if a student is signed in, check if they're a pre-order student and if so, let them take the course. If they're not a pre-order student, display the pre-order button.