Currently most used dcaccount: scheme is accepting just the domain name, e.g. dcaccount:example.org. It is also possible to have an URL in there, but it is less used now, the issue is only about the new scheme with a domain name.

We need a way to preload an IP address in there, so onboarding can work without the DNS. Something like dcaccount:example.org?a=127.0.0.1. IP addresses in this case should be injected into DNS cache as if it was just resolved. Ideally only for configuration in-memory, so it is not saved if configuration failed and the same database is reused for another relay, but if it's too difficult then just injecting it into the database as successful resolution is ok.