return descriptive answers for RFC 6761 zones
Right now, the policy by default blocks queries for RFC 6303 & 6761 zones and answers them with rcode=NXDOMAIN and SOA RR in authority section with names like blocked.
in it.
This confuse less experienced users, so we could add an explanatory TXT record into ADDITIONAL section, and document this using terms like "automatic empty zone" from BIND and Unbound's equivalent.
Links: https://www.iana.org/assignments/special-use-domain-names https://www.iana.org/assignments/locally-served-dns-zones/locally-served-dns-zones.xhtml