This is so that our permissions aggregation query can use MAX(column)
which exists and works in both postgres and sqlite, as opposed to having
some conditional aggregate function that we use depending on our
backend.
Calling `.after` on a dateutil.rrule object that has an UNTIL clause
performs very poorly if the interval is low and the start time is a long
time ago. This patch replaces two test cases where we were using a
minute interval with a fixed start time of (currently) 2 years ago,
which resulted in aproximately 40s of execution time to simply evaluate
`.after(now())`. Replacing these two tests with tests that start from
"yesterday" while keeping the same INTERVAL and UNTIL settings
eliminates this unnecessary slowdown while maintaining the spirit of the
original tests.
Akita Noek