Function gather_user_metadata 

async fn gather_user_metadata(
    services: &Services,
    sender_user: &UserId,
    sender_device: Option<&DeviceId>,
    room_id: &RoomId,
    filter: &FilterDefinition,
    timeline_pdus: &[(PduCount, PduEvent)],
    receipt_events: &[(OwnedUserId, Raw<AnySyncEphemeralRoomEvent>)],
    since: u64,
    initial: bool,
    timeline_changed: bool,
    encrypted_room: Option<bool>,
    since_shortstatehash: Option<ShortStateHash>,
) -> UserMetadata