Function stripped_state 

async fn stripped_state(
    services: &Services,
    sender_user: &UserId,
    room_id: &RoomId,
    membership: Option<&MembershipState>,
) -> StrippedRoomState

The stripped state MSC4186 sends for an invited or knocked room.

For a knocked room this is the summary stored with the knock, ending with the user’s own knock event, so a client can present a room this server is not in. An empty knock summary is omitted, since a client reading the user’s membership from it would take the room for an invite.