* Use nonce in data messages to de-dupe SendData API.
With API retries, it is possible that some data messages are sent
multiple times. Check the nonce (if present) to de-dupe data messages
before forwarding it to the clients.
* add nonce to UserPacket
* defer unlock
* 128-bit UUID as nonce
* - UUID nonce
- make a UserPacketDeduper module for easier re-use.
* deps
* feedback
Raja Subramanian