Interface responds to `network` but not to `network6`
The Nic class has a method
network which is delegated to
subnet, but no method
network6 (which should be fetched from
subnet6. This is no breaking bug, but rather inconsistent.
Fixes #19991 - Add network6 to nic model
This adds the method `network6`, delegated to the `subnet6` relation.
Because the `delegate` methods does not support completely renaming a
method, I use a combination of delegate and alias. I updated the
definition for `network` (the v4 equivalent) to be consistent.