OAuth: resync RemoteRepository weekly for active users

[humitos]

Trigger a daily task to compare user's last login isoweekday with today's
isoweekday for all active users. If they matches, we resync the
RemoteRepository for this user.

This logic is the same as "resync RemoteRepository once a week per each user".

We consider active users those that have logged in at least once in the last 90
days.

Related: #8229
Related: #9409

[humitos]

Note that this is about 2k users to resync per day, which I don't think it's terrible, but it's definitely a lot more than what we are doing currently:

In [75]: Counter(
    ...:     User.objects.annotate(weekday=ExtractIsoWeekDay("last_login"))
    ...:     .filter(last_login__gt=three_months_ago, socialaccount__isnull=False)
    ...:     .order_by("weekday")
    ...:     .values_list("weekday", flat=True)
    ...: )
Out[75]: Counter({1: 1749, 2: 1873, 3: 1927, 4: 1749, 5: 1603, 6: 1025, 7: 942})

This may stress our web-celery ASG a little. We could split those 2ks into 10 and trigger ~200 tasks every hour instead of 2k at the same time. Does it worth trying this as-is and splitting it later if we found that's too many tasks at once?

There are some improvements to do here too:

• ignore GH organization with plenty of repositories (see GitHub OAuth: skip conda-forge organization when syncing #8979)
• mark users with revoked permissions for our app to not resync until they reconnect
• migrate to GH Application that allows us to receive webhooks instead (this migration is not trivial, as we found out)

[ericholscher]

This looks like a good approach, but I'd much rather tie up 1 celery process and take a long time vs. totally block celery.

[humitos]

There is an unrelated problem with the docs,

/home/circleci/project/docs/user/guides/jupyter.rst:306: WARNING: unknown document: poliastro:gallery