I ran the `bin/console spdx --fix` with different strategies for
different files. For most of the core classes, since they've been
drastically rebuilt, I've run it with the `git-blame` strategy, for for
the `src/Validators`, in which the API changed completely but the logic
remains the same, I use the `git-log` strategy.
- Changed Property so it doesn't have an unreachable line anymore.
- Rename ValidatorTest to ValidatorBuilderTest to better reflect
the source.
- Added missing tests for KeyExists's ArrayAccess support.
- Added tests for using custom exceptions.
This commit introduces REUSE compliance by annotating all files
with SPDX information and placing the reused licences in the
LICENSES folder.
We additionally removed the docheader tool which is made obsolete
by this change.
The main LICENSE and copyright text of the project is now not under
my personal name anymore, and it belongs to "The Respect Project
Contributors" instead.
This change restores author names to several files, giving the
appropriate attribution for contributions.
