This commit introduces the `Trimmed` validator that ensures a string
cannot start or end with a list of specific values.
The default values used are a selected list of Unicode invisible
characters.
To support this change, the StartsWith and EndsWith validators were
modified so they can also support multiple values to check for.
While StartsWith and EndsWith are more generic, and also perform
start-of-array and end-of-array kinds of checks, Trimmed is more
focused on string inputs, which tailors to a more specific use
case.
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.
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.
