begin converting DNSSEC validation tests from shell to python,
and simplify the name servers used in the test.
ns4, the name server used for validation tests, is now configured
using jinja2 templates.
ns8, which was previously used for testing unsupported, disabled
and revoked keys and trust anchors, has been removed. we now
use a jinja2 configuration in ns5 for this purpose.
the configurations in ns7 and ns6 didn't conflict with one another,
so the two servers have been merged into one.
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.
More specifically: ignore configured trusted and managed keys that
match a disabled algorithm. The behavioral change is that
associated responses no longer SERVFAIL, but return insecure.
