Follow-up to https://github.com/element-hq/synapse/pull/20407, which
added the `excluded_user_ids` option without enforcing it. This makes
legacy `/sync` respect it: users listed in a room's `excluded_user_ids`
no longer get that room through the synthetic join. They can still read
it, as it is world-readable.
The cached lookup now maps room ID to config ID, so the per-user filter
runs in memory and adds no database query to `/sync`.
`get_server_announcement_room_ids()` is kept as a wrapper, so the
stacked PRs are unaffected.
Known limitation, documented in the config docs: changing the list does
not update rooms that clients already have. A newly excluded user keeps
the room, which stops updating. A user removed from the list gets new
events without the room's state until their next initial sync. I think
that's an okay limitation for now, as we don't really expect this list
to be used for real users
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Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
