TSIG for PowerDNS (and Yadifa)

[mdavids]

https://workbench.sidnlabs.nl/transfers.html says "NOTE: Yadifa and PowerDNS don't have TSIG keys configured just yet", but meanwhile PowerDNS has support for it, so we should add that (https://doc.powerdns.com/authoritative/tsig.html).

The same probably applies to Yadifa: https://www.yadifa.eu/sites/default/files/yadifa-reference-manual.pdf