this fixes the disconnect loop when the server has just started by
waiting for the connection to open before subsribing to events.
also includes other improvements:
- rename types to interfaces
- allow to input single receiver for signal
- use discovery api to check for upgrade path instead hard coded one
Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>
next try after #18153 without any external dependencies and only
supporting websocket. missing tests and necessary documentation but will
work on those after initial comments if this would be proper way to go
forward. already planning for the notification plugins on top of this.
Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>
Marek Libra