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.
When configuring the same dnssec-policy for two zones with the same
name but in different views, there is a race condition for who will
run the keymgr first. If running sequential only one set of keys will
be created, if running parallel two set of keys will be created.
Lock the kasp when running looking for keys and running the key
manager. This way, for the same zone in different views only one
keyset will be created.
The dnssec-policy does not implement sharing keys between different
zones.
