Change default TTLsig to one week
Commit dc6dafda allows larger TTL values in zones that go insecure, and ignores the maximum zone TTL.
This means that if you use TTL values larger than 1 day in your zone, your zone runs the risk of going bogus before it moves safely to insecure.
Most resolvers by default cap the maximum TTL that they cache RRsets, at one day (Unbound, Knot, PowerDNS) so that is fine. However, BIND 9's default is one week.
Change the default TTLsig to one week, so that also for BIND 9 resolvers in the default cases responses for zones that are going insecure will not be evaluated as bogus.
This change does mean that when unsigning your zone, it will take six days longer to safely go insecure, regardless of what TTL values you use in the zone.