Support Live Mode in the Pickup Protocol

[FabioPinheiro]

Live Mode

Live Mode in the Message Pickup Protocol

• This feature is blocked by Support WebSockets Transport for DID Comm  #144

Value brief

The main is to avoid polling to check if there are any new message
This will remove the overhead of individual requests for polling (status-request / delivery-request).

This will also greatly improve use cases of near-real-time communication with mediators.

Implementation notes

The Live Mode is defined on Message Pickup Protocol.
Only registered DID (in the mediator) can enable this mode. After the mediator replies with a mediate-grant

We need to keep internal metadata about the WebSockets:

• Who is on the other side of the WebSockets? (Will be add in Support WebSockets Transport for DID Comm  #144)
  • Unknown - there is no previous message.
  • Set[DID] - one or more subjects based on the previous encrypted message sent.
• Which DIDs are enabled Live Mode on this WebSocket?

The logic to start the action of pushing any new message will be added end of the ForwardMessageExecutor, the last step after storing. In this case, the MessageDispatcher needs to be overridden to only use a specific websocket(s), so it doesn't fall back Transport (EX: it may discover that the WebSocket is broken).