Directly lookup local membership instead of getting all members in a room first (get_users_in_room mis-use)

[MadLittleMods]

Directly lookup local membership instead of getting all members in a room first (get_users_in_room mis-use)

See #13575 (comment)

Dev notes

get_user_in_room_with_profile (not implemented)
get_subset_users_in_room_with_profiles

check_user_in_room
get_local_current_membership_for_user_in_room

check_user_in_room_or_world_readable

is_user_in_rooms

---

member\S*room
membership\S*room
join\S*room
user\S*room

Pull Request Checklist

• Pull request is based on the develop branch
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• Code style is correct
  (run the linters)

[MadLittleMods]

There are several of these is_server_notices_room kind of functions but this PR doesn't deduplicate them.

[MadLittleMods]

This is similar to check_user_in_room that is in synapse/api/auth.py but that one has some specific logic and can check for leave so I decided to leave it as-is.

synapse/synapse/api/auth.py

Lines 69 to 119 in a25a370

	async def check_user_in_room(
	self,
	room_id: str,
	requester: Requester,
	allow_departed_users: bool = False,
	) -> Tuple[str, Optional[str]]:
	"""Check if the user is in the room, or was at some point.
	Args:
	room_id: The room to check.
	requester: The user making the request, according to the access token.
	current_state: Optional map of the current state of the room.
	If provided then that map is used to check whether they are a
	member of the room. Otherwise the current membership is
	loaded from the database.
	allow_departed_users: if True, accept users that were previously
	members but have now departed.
	Raises:
	AuthError if the user is/was not in the room.
	Returns:
	The current membership of the user in the room and the
	membership event ID of the user.
	"""
	user_id = requester.user.to_string()
	(
	membership,
	member_event_id,
	) = await self.store.get_local_current_membership_for_user_in_room(
	user_id=user_id,
	room_id=room_id,
	)
	if membership:
	if membership == Membership.JOIN:
	return membership, member_event_id
	# XXX this looks totally bogus. Why do we not allow users who have been banned,
	# or those who were members previously and have been re-invited?
	if allow_departed_users and membership == Membership.LEAVE:
	forgot = await self.store.did_forget(user_id, room_id)
	if not forgot:
	return membership, member_event_id
	raise UnstableSpecAuthError(
	403,
	"User %s not in room %s" % (user_id, room_id),
	errcode=Codes.NOT_JOINED,
	)

[MadLittleMods]

My guess is the difference between cached calls of get_users_in_room

[MadLittleMods]

Thanks for the review @clokep and @reivilibre 🐮