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.
Given the characteristics of the three timestamps involved in file
modification time checks in the cds system test (each one is an hour
apart from the next), reduce the resolution of these checks to 1 minute.
This will prevent intermittent false negatives caused by exceeding the
currently allowed difference of 9 seconds between file modification
times without making the test moot.
Also note that by using abs(), checkmtime.pl allows the cds system test
to pass when the modification time of the checked file is less than an
hour (or two hours for the second check) in the past. This should never
happen, so remove abs() from the condition checked by checkmtime.pl.
4757. [func] New "dnssec-cds" command creates a new parent DS
RRset based on CDS or CDNSKEY RRsets found in
a child zone, and generates either a dsset file
or stream of nsupdate commands to update the
parent. Thanks to Tony Finch. [RT #46090]
