Testing different PHP versions

In the past, one could test against different version of PHP.
The new system does not support that, I believe.

When developing, I work in 1 version, so, indeed, sometimes a PHP8.3 feature was built in, innocently.
Now, I have several issues for this and other module that should be postponed, until 8.1 and 8.2 are not supported anymore.

If you have any tests failing, I am happy to revert some code.
Please create an issue in that case.

I now see thisis possible with gitlab:
- https://lostcarpark.com/drupal/future-proofing-your-module-and-dependenc...
But it requires phpunit tests for full code coverage, and that is missing in my modules.