SRV and MX _could_ have more structure (priority, etc). not sure the best path there (option submodule, i guess).
records
extraConfig
i'll be adding special options for records
machines
hosts
- shorter. - congruent with `nixos-rebuild .` choosing what to build based on `hostname`. - more widely used within other nix repos i've seen. - more accurate in the case that i migrate a host to a different machine (which i plan to do with servo).