If true, enables the use of NSEC3 together with DNSSEC on the zone.
Combined with setting dnssec_presigned to true, this enables the use of
NSEC3 records when transferring in from an external provider.
If dnssec_presigned is instead set to false (default), NSEC3 records will be
generated and signed at request time.
See DNSSEC with NSEC3 for details.