Editing Trip end date to be earlier than Plan's start dates

[Vielheim]

Currently it's possible to do the above, not sure if we want it though

• The issue is that Trip does not know anything about its plans. So when we want to edit a trip, it just uses its own boundaries for start and end dates.

Would be preferable when we edit trip:

• Start date is in range of: min(current date, earliest plan's start date) to plan's earliest date
• End date is in range of: max(trip's end date, latest plan's end date) to any date after that

I tried to do it but it was quite hard to create the picker for the boundaries