This was originally added in a97b642289 as
part of https://git.pleroma.social/pleroma/pleroma/-/merge_requests/1818
with the hope/intent of using it to hide DMs by default from timelines.
This never came to be with thisd parameter still being unused today in
al of akkoma-fe, pleroma-fe, Husky, pl-fe, Mangange, fedibird-fe and
masto-fe. Given thypically only a small percentage of posts are DMs,
as well as issues with the SQL function and index used to implement this
a removal likely won't bother anyone while allowing us to clean up
bugged code and improve actually used functions.
While unlikely, we don't have a way to ascertain for sure whether there
are still users so for now only drop it from API Spec which leads to
the parameter being stripped out before processing and keep the actual
logic. If any users exist and complain we can easily revert this, if not
we will follow up with a proper cleanup.
This reduces both the size the indexes take on the disk
and the overhead of maintaining it since it now only
needs to be updated for some entries.
For the email index restriction queries needed to be updated,
the last_active_at index is used only by one query which already
also restricted by "local" and for the remaining restrictions
no query adaptations are needed.
