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.
This test is very simple, two nameserver instances are created:
- ns4: master, with 'minimal-responses yes', authoritative
for example. zone
- ns5: slave, stub zone
The first thing verified is the transfer of zone data from master
to slave, which should be saved in ns5/example.db.
After that, a query is issued to ns5 asking for target.example.
TXT, a record present in the master database with the "test" string
as content.
If that query works, it means stub zone successfully request
nameserver addresses from master, ns4.example. A/AAAA
The presence of both A/AAAA records for ns4 is also verified in the
stub zone local file, ns5/example.db.
