General car renting fixes

[Armadillan]

Changes based on my (Vic, BilF 25/26) opinions:

• Personal bookings are never automatically confirmed when created.

General bug fixes:

• Non-admin bookings are no longer automatically confirmed when updated.
• Council bookings are no longer autmatically unconfirmed on update (for any reason, including falling outside of school hours).
• Fixed time zone shenanigans when checking for bookings outside of school hours.

[Armadillan]

I'll write some tests tihi

[Armadillan]

Changed tests to always expect personal bookings to be unconfirmed and council bookings to be confirmed, irrespective of time (as per my spec, see pr comment). Also added some new tests.