Support saving schedules with Kerberos login

[SuperSonicHub1]

Schedules can currently only be shared across different machines through taking advantage of the "Share" feature of Hydrant. My current setup is editing a Google Keep note with the URL whenever I edit my schedule, which is hilariously scuffed and error-prone.

This feature, if implemented, would allow a user to save their schedules to a database by logging in with their Kerberos identity, making them accessible across multiple devices. Saving schedules to local storage should still be an option for those who aren't MIT students.

[cjquines]

OOF this one is going to need an actual backend, which to be clear hydrant currently does not have.

probably could be integrated into the courseroad backend but im not superfamiliar with how that works; @sipb/courseroad-dev would be more familiar

[psvenk]

I believe that the FireRoad server has a mechanism for saving schedules, as the FireRoad app has this functionality. (CourseRoad uses the FireRoad server to store schedules and also does not have its own backend.) Ideally we should aim for interoperability between Hydrant and the FireRoad app, just as CourseRoad interops with the FireRoad app.

This would also entail moving from fireroad-dev to fireroad (prod).