new: usr: Add "zone has but is not served by" warnings
requested to merge 4370-check-that-a-zone-is-served-by-ipv6-servers-if-it-has-aaaa-records into main
Check that zones with AAAA records are served by IPv6 servers and that zones with A records are served by IPv4 servers. This is an often accidental error when configuring IPv6 services and prevents IPv6 only sites from retrieving the addresses without falling back to IPv4. The end stage of IPv4 also runs to the risk of having IPv4 services that are not reachable from legacy IPv4 only networks.
Closes #4370
Edited by Mark Andrews