We are grafting on an unsigned zone "example.internal" where the higher
zone (".") is signed and would otherwise cause named to synthesise a
NXDOMAIN for example.internal. We prime the cache by performing a
lookup for "internal" and then lookup "example.internal".
This commit converts the license handling to adhere to the REUSE
specification. It specifically:
1. Adds used licnses to LICENSES/ directory
2. Add "isc" template for adding the copyright boilerplate
3. Changes all source files to include copyright and SPDX license
header, this includes all the C sources, documentation, zone files,
configuration files. There are notes in the doc/dev/copyrights file
on how to add correct headers to the new files.
4. Handle the rest that can't be modified via .reuse/dep5 file. The
binary (or otherwise unmodifiable) files could have license places
next to them in <foo>.license file, but this would lead to cluttered
repository and most of the files handled in the .reuse/dep5 file are
system test files.
construct a test zone which contains a minimal NSEC record,
emit priming queries for this record, and then check that
a respose that would be synthesised from it isn't.
