Scenario:

• connected to wifi (ipv4-only), and wwan (ipv6, ipv4 doesn't matter)
• lookup domain that only has AAAA record(s), no A records in DNS
• dnsane will currently filter out all AAAA records, since wifi is the primary connection and it doesn't support ipv6

There should be an option to allow sending back a response if filtering it would result in an empty response / no answer records, so that (in the example scenario above) it's still possible to reach domains with only AAAA records over the non-primary connection (wwan). It kinda breaks the original intention of filtering in dnsane, but I think there are legitimate reasons to allow this. Adding it as an option / cmdline param will let users choose which behavior they want, the default should continue to be the more aggressive current behavior of always filtering unsupported record types.