Add validation constraints to all system.* simple config (except system.rss)

system.rss.yml is mostly useless and should be removed in 🐛 Views RSS view mode settings are completely broken Needs work

Thank you, @longwave! That's a relief 😄 I'll push that forward too then 👍

Down to a single failure, for AjaxTest::testAjaxFocus(). I'll let that one slide for now and move on to the next system.* simple config 👍

Aha, that passed — so AjaxTest must be prone to random failures…

That "dear committer" note on the MR updates code introduced by #2870878: Add config validation for UUIDs → 6.5 years ago that is now obsolete 🥳

Wim Leers → changed the visibility of the branch 2300677-jsonapi-config-entities to hidden.

The Needs Review Queue Bot → tested this issue. It no longer applies to Drupal core. Therefore, this issue status is now "Needs work".

This does not mean that the patch necessarily needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

Consult the Drupal Contributor Guide → to find step-by-step guides for working with issues.

Down to a single failure triggered by the validation now running for system.theme — quite a few test coverage bugs uncovered! 🚀

Ok, im going to try and rebase this.