Verify reservations one last time before startDate occurs

[karllindmark]

If we want to somewhat "reliably" determine if we've reserved a spot at a class and actually gone through with it, we kinda need to do "one last check" before the actual class begins. Given the fact that the user can't remove a reservation within one hour from startDate, it should be "good enough" for us to know whether or not we should keep it on-device as a "past reservation".

So, basically, pseudo-wise:

1. Reserve a spot
2. Schedule a "verification request" within an hour from startDate
3. Keep/remove the workout from the local database