Function invite_permitted_room 

async fn invite_permitted_room(
    services: &Services,
    user_id: &UserId,
    room_id: &RoomId,
    filter: &InviteFilter,
) -> bool

MSC4155: whether a stored invite may be served to the invitee.

The verdict is the recipient’s own, judged against the sender of the stripped invite membership event. Unreadable invite state takes the same verdict as the sender-less case below, since neither can name a sender.