Registration deadline

[dorodere]

In order to book the bus early enough, make all transactions and the like, you might want to wish to have a configurable deadline per drive. After this deadline no more registrations can be made, no matter if the cap is reached or not.

Currently the deadline is hardcoded to be the day of the drive, at 00:00 UTC:

https://github.com/dorodere/komplett-normale-busliste/blob/37e479201def703088639c8a4a74ecfb6325642e/src/main.rs#L162-L168

This probably needs to be configurable in a way that matches both drives per weekend at once, so for example if one drive is on Friday and one on Monday, but the user set Thursday 00:00 UTC as deadline, both drives need to respect the case where the deadline might be in another week. In other terms, every drive needs to watch out about what's the last time matching this deadline is, and not necessarily the week the drive is in.

[dorodere]

Rough todo when implementing:

• [x] add a date field for each drive, containing the deadline timestamp
  • bonus: move all drive stuff into new subpage named Drive management or the like already done in #12
  • probably best stored in an INTEGER DATETIME fits better
• [X] add a default weekday setting for the deadline, somewhere (probably in a settings page)
• [X] when adding a drive,
  • calculate which concrete date the default weekday (if not null) corresponds to by "backtracking" which was the last time that weekday was
  • use that concrete date as deadline
• [x] when asked to register,
  • check if the current time is larger than this deadline (if not null)
  • possible optimization for the future: cache whether the deadline passed already for a drive
  • if that time check should fail, flash out