async fn check_existing_txnid(
services: &Services,
sender_user: &UserId,
sender_device: Option<&DeviceId>,
txn_id: &TransactionId,
) -> Option<Result<Response>>Expand description
Replays a stored notice response for the requesting user and device.
Empty transaction data belongs to an incompatible endpoint; invalid event IDs indicate corrupt stored data rather than a fresh transaction.