Compatibility Drupal 10.3^

Thanks for the report. I will take a look at it during contribution day at DrupalCon this Friday.

I applied the patch in #1 and it fixed the reported issue, but I'm seeing a subsequent error:

1. Go to the add Country form
2. Populate the field values, choose "GB" for Country Code
3. Submit

Expected results: The form is submitted and the Country is created.

Actual results: Validation error on Country Code field with message "The value you selected is not a valid choice."

It looks like core added a CountryCode constraint in 10.3 (CR here: [#3441838] ) which conflicts with the CountryCode constraint used in this module. Core's one appears to take precedence, but its validation isn't picking up the value properly from this field, and rejects in all cases.

Proposed Solution: The core CountryCode validator is a more specific validation (i.e. tests against the actual list of country codes). This module should probably use that.

For expediency, I've just renamed this module's country code constraint. I've raised a MR that includes both the patch from #1 plus this change.

I've updated gitlab-ci.yml so it only gets tested on Drupal 10.3, and made various other linting fixes. Pipeline passes now. Please review.

Added changes for Drupal 11 compatibility. @jamsilver Can you give this another review? Afterward, I will merge and tag a new release.

I've done a quick test on Drupal 10.3 and a (very quick) test on Drupal 11.0.6 and it seems to work. I saw one thing on the MR that I think needs to be changed (see other comment).

Have tested on D10 and (briefly) on D11.1. Suggest merging and fixing any bugs as folk find them.