Add API function to receive notifications [$300]

[woodser]

This issue requests adding a new API function to receive notifications.

This API call will feed the UI notifications:

The following function is requested as an addition to HavenoDaemon.ts (feedback welcome).

API Function	Return	Description
havenod.onNotification(listener: function)	void	Invokes the given function on each new notification. Usage: await havenod.onNotification(function(notification: Notification) { ... });

How to implement

We want the client to receive a push notification from the gRPC backend for each notification.

We intend to use gRPC streaming and/or websockets to achieve push notifications. Here is some documentation to get started:

• Streaming example using gRPC web
• Server-side streaming example
• Using websockets with gRPC

Follow these instructions to add and test new API functions end-to-end.

[github-actions]

There is a bounty on this issue, the amount is in the title. The bounty will be awarded to the first person(s) who resolves this issue. Read the full conditions in the 'bounties.md' file. If you are starting to work on this issue, please write a comment here, so that we can assign the issue to you and avoid duplicated work.

[KritR]

I’d be interested in working on this.

[erciccione]

Thanks @KritR. I'm assigning the issue to you. Please keep us updated :)

[erciccione]

Hey @KritR. Could you share an update on how things are going? :)

[LumnitzF]

I would like to work on this feature.
Open questions:

1. What fields should the Notification provide?
2. Should multiple listeners be supported, or only one per daemon?
3. Should there also exist the possibility to remove a message listener again?

[erciccione]

Of course, assigning it to you. Thanks @LumnitzF! :)

[erciccione]

Core: #209
UI: https://github.com/haveno-dex/haveno-ui-poc/pull/62

[LumnitzF]

@erciccione / @woodser Could you please send the bounty to:

85TXCCFva9ULot4D3bvBpeJ6aMHyUeKJCNeeLAXhobL2C6dvZAFKpjwHKfeeQmbrRoYcf4DddkAWzRRTGqwAS5vu4efa1nV

Thanks in advance :)

[erciccione]

Reward sent! @LumnitzF please comment here when you receive it :)

[LumnitzF]

@erciccione Received the bounty. Thank you!

[woodser]

Thank you!