The activity was incorrectly scheduled with a deadline as the now in UTC while
the state was computed using "today" in the user's timezone.
This made the nightly test fail (run at 23:30 UTC with the user in UTC+2).
Use context_today instead of today for all activity_schedule calls
To make it easier, use on the context_today default value instead of setting
context_today everywhere (which is more error prone in the future)
Never use datetime, only date objects
add a warning to detect potential errors when passing a datetime
Closes#26411
Martin Trigaux
d97e69ff02