DESEC: should support setting nameservers

[OdyX]

Is your feature request related to a problem? Please describe.
Now that desec.io allows using European TLDs (see https://talk.desec.io/t/european-nameserver-tlds-now-available/1550 ), it would be nice to be able to set these in the zone and registrar.

Describe the solution you'd like
This code should result in the default NS records being updated to the explicitly-defined TLDs:

D("example.com", NewRegistrar("dohcloudflare"),
        DnsProvider(DSP_DESEC),
        DefaultTTL(3600),
        NAMESERVER("ns.desec.ch."),
        NAMESERVER("ns.desec.cz."),
END);

Describe alternatives you've considered
Of course, I can go in desec webinterface and set these manually, but that defeats the point.

On a related note, see desec-io/desec-stack#1168

[tlimoncelli]

CC @D3luxee (maintainer of deSEC)