booking rules:

(1) Per user only 2 bookings per week in advance (1 booking is one shift: morning or afternoon).

(2) Devices are only booked for 3 weeks in advance.

(3) Exception for rule 1: In case the morning shift is not booked till 13:00 for the following day, do so. In case the afternoon shift is not booked till 08:00 for the current day, do so.