async fn gather_device_list_updates(
services: &Services,
sender_user: &UserId,
room_id: &RoomId,
timeline_membership_changes: Vec<(MembershipState, OwnedUserId)>,
state_events: &[PduEvent],
initial: bool,
since: u64,
next_batch: u64,
) -> (HashSet<OwnedUserId>, HashSet<OwnedUserId>)