Mastodon API: ensure the notification endpoint doesn't return less than the requested amount of records unless it's the last page

Inspired by https://git.pleroma.social/moonman/emoji-stealer-mrf/-/blob/master/steal_emoji_policy.ex

Apparently some instances have local users with local ap_ids
that are marked as local: false. Needs more investigation into how
that happened.

In the meantime, the skeleton migration was patched to just ignore
all known ap ids, not just locals. Doesn't seem to slow down the migration
too much on patch.cx

Closes #1746

as opposed to memory currently in use

Mastodon API: do not create a following relationship if the corresponding follow request doesn't exist when calling `POST /api/v1/follow_requests/:id/authorize`