Outgoing interface for notifies and transfer requests
listen is used to specify one or more IP addresses where the server listens for incoming queries.
Currently there doesn't seem to be a way to specify outgoing interface for notifies and transfer requests, similar to what NSD does with outgoing-interface and BIND with notify-source and transfer-source.
Has an option to specify outgoing interface for notifies and transfer requests been considered and abandoned for Knot DNS?