Comment 1 for bug 1562919

It's actually more complicated:

When foo.example.com is a domain that we know about, then fqdn=foo.example.com needs to separate into (name=@, domain=example.com)

When the domain bar.example.com is created and RRsets exist for bar.example.com, dnsresource.{name,domain} need to be updated to accept the insertion.

There should never be entries (name=baz, domain=example.com) when the domain baz.example.com exists in Domain.