[knot-dns-users] Adding ALIAS local resolution to knot-dns

Hi, Fastmail has been running Knot for a few years now. Thank you for such excellent software! I'm new to this list, and new to the Knot codebase, but I'm an experienced C developer and have been working on Cyrus IMAPd (a mostly C codebase) for many years. We have hundreds of thousands of domains, and currently they all have the same set of service IPs compiled into them. This has generally been fine - setting up a new server takes an hour or so to build all the domains, but we just wait until it's done then bring it into rotation. Our current challenge -- we want to be able to transfer everything to a new IP range quickly for datacenter failover. Rebuilding every zone is too expensive for this. I looked at a few different issues and (along with Claude) figured that it wasn't much work to extend the ALIAS type to follow the pointer to another zone inside the same server and return the records from that. I have an initial pass at: https://github.com/fastmail/knot-dns/tree/local-alias-synth For now I've kept it as separate commits showing the evolution of the idea as I've tested it more and thought through how I want it to interact (basically any ALIAS get substituted with the contents of the name it points to, so you can mix and match them all sorts of ways). I'm very happy to engage on testing and modifying this code to match what the upstream project wants; or revisit the approach if this doesn't match your vision. I just need something that has these properties, and this seemed a good way to get there. Thanks, Bron.