Prepare the module for D9

I ran drupal-check on this module and found an issue:

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  Line   tests/src/Unit/Logger/LoggerTest.php
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  22     Call to deprecated method getMock() of class Drupal\Tests\UnitTestCase:
         in drupal:8.5.0 and is removed from drupal:9.0.0.
         Use \Drupal\Tests\PhpunitCompatibilityTrait::createMock() instead.
 ------ -------------------------------------------------------------------------

Need to update composer.json too.

In #3032946: Update dependency monolog/monolog to version 2.x there's currently the discussion, if switching to monolog library 2.x should be done on a new 2.x branch (mainly because this move would also mean dropping PHP 5.x support).

I'd propose the following approach, if a 2.x branch will be opened anyway: do not commit this in 1.x branch, as this isn't meant for D9 anyway. And in a 2.x branch, we should raise requirements even higher to 8.8.3 and start a semantic versioning branch instead. Here's an example of a module, where I have already started a new branch for semantic versioning (and you need a new branch for this step anyway): https://www.drupal.org/project/commerce_order_autovalidate

I vote we get this in, so people can start upgrading their sites?

If we have to wait for a 2.x branch and development to start, there is no way we can upgrade any of our sites to drupal 9. A simple fix as the first fix seems like a good start.

Tested on Drupal 9, works like a charm

This is a tweak to composer.json. We don't need to specify a core version there.

Committed and pushed to 2.x branch
Thanks!

@lussoluca this issue was originally for 1.x branch, could we also have this applied there. Thanks!

If 1.x will not be supported for D9 lets communicate it on the project page.

Yes, we'll only support 2.x on Drupal 9. I've updated the project page