Help topics module - documentation page not found

Thanks @rksyravi! The Help Topics module is experimental, so its documentation might not be completed until it is closer to stable. That said, we should probably at least create a stub page or check that the URL is correct.

Does it actually make sense to make that page? The plan is for the Help Topics module to be merged into the Help module, so we do not really want that documentation to exist when the module is stable. We can make a stub page for now but we would want it to go away...

We could also put in a redirect from that URL to the modules/help docs page, and a note at the top of that page about Help Topics beta?

OK, there are actually two problems here.

First: The link in the hook_help for help topics module should be https://www.drupal.org/documentation/modules/help_topics, not https://www.drupal.org/modules/help_topics as it is now.

Second: the correct link didn't go anywhere... I think it should probably be redirected to
https://www.drupal.org/docs/develop/documenting-your-project/help-topic-...
which is a docs page about the new help topics system. So, I've put that redirect in.

We also need a patch to fix the link in help_topics.module, so here is that.

Looks good to me.

+1 rtbc, https://www.drupal.org/documentation/modules/help_topics

Fixed IS

Unrelated test failure. I assume this one is known:

Drupal\KernelTests\Core\Action\SaveActionTest::testGetDerivativeDefinitionsassertArraySubset() is deprecated and will be removed in PHPUnit 9.
/var/www/html/vendor/phpunit/phpunit/src/Framework/TestResult.php:691

Committed and pushed 63cdee3511 to 9.0.x and c179a28bb0 to 8.9.x and 6e9b99da12 to 8.8.x. Thanks!

Closed a duplicate, adding credit here.