WebSocket Notification Binding (move to split TS)

HTTP notifications are not always suitable for clients, e.g. browser clients, and also often cannot be used due to firewalls or NAT (network address translation). WebSockets provide an efficient solution, where the connection is set up by the client (on subscription), and then the connection is kept alive and notifications are sent through this connection, avoiding the overhead of creating a new connection each time a notification is to be sent.