Follow-up from "Draft: Resolve "Reimplement notification system on base of new calendar system""

The following discussion from !360 (merged) should be addressed:

• @yuha started a discussion:

  FIXME: Hide preferences related to the time notifications are sent conditionally (is this even possible?), depending on the trigger mode selected

changed milestone to /AlekSIS%"[NLnet #1 (closed)] Implement timetable notifications"

added part::backend label

assigned to @yuha