avoid error log name resolution

[tobit6795]

not that heavy in my opinion but maybe something that can be improved.

this error happens because of that the domain is not provided as fqdn in the fritzbox configuration menu for ddns.

[wernerfred]

I figured that out too a while ago. I think you are right and the only way to avoid this kind of errors is to provide the fqdn as the domainname. Therefore we need to adapt the logic in the go script that runs the api that it is aware of a fqdn instead of a subdomain. For the sake of consistency we also should change the input environment variables to fqdns instead of the subdomains. That would result in breaking the backwards-compability and a bump of the major version.