Notifications subsystem

[CMCDragonkai]

The notifications subsystem allows nodes from different gestalts to send messages to each other.

This is the way that users can tell other gestalts that they have shared a vault with them.

• Number of messages must be limited possibly 10,000, afterwards the messages are dropped
• Must use the ACL notify permission action
• Need to consider that once a message is read by any, that message is kept around in the notification queue, but is considered to have been read

See https://gitlab.com/MatrixAI/Engineering/Polykey/js-polykey/-/merge_requests/204

Specification (from node notifications MR!161 in js-polykey):

• Agent GRPC exposes sendMessage and readMessage.
• Node GRPC exposes receiveMessage.
• Client will trigger sendMessage to Agent.
• Agent then connects to the node using NodeId and triggers a Node GRPC which is recieveMessage.
• Other Agent will push messages to the Notification object.
• Other Client can now shift all messages from the Notification object using readMessage that is a GRPC stream.

Note: gPRC calls should follow style outlined in #218

TODO

• New domain notifications
• Create Notification class
• Inject ACL, DB, NodeManager as dependencies
• Create the send and receive calls
• Make a limit on the number of messages allowed
• Check the ACL for permissions
• Create the Agent GRPC calls to receive messages
• Use the NodeManager to send out messages
• Create tests for Notification class
• Create pk notifications sub commands to introspect notifications
• You might want to have a "read" status attached to each message indicating
• Create tests for the pk notifications

[CMCDragonkai]

When using the NodesManager, this is just making a call to send a message.

The Notifications will probably need the NodeManager as a dependency injection.

[CMCDragonkai]

You do need to use the ACL to see if the there is a notify permission allowed on nodes trying to contact you.