Make compatible with Drupal 11

I got the tests to pass by reverting the category previously set. Ready for review, and I can verify that this is working for me in a relatively fresh install of Drupal 11.

I am mulling over whether we should cutover to a 3.2 release for this, since support for D9 is (appropriately) dropped in this MR.

If you foresee wanting to continue support for sites running Drupal 9 (or Drupal 10.1 or 10.2), then merging this into a new 3.2.x branch would be the way to go. Seems like a sensible approach.

Ok, let's plan on that. I'd like to do a 3.1.5 release within the next few days, then branch 3.2.x off at that point. Then you can re-open your MR against that new branch and we'll do a 3.2.0 release immediately after committing this. If you see any issues with this timing or plan please comment.

I think there's a middle step we can take here. I went ahead and created a 3.2.x branch, and have already updated the MR to target that. I believe it should be safe to marge it into the new branch, and then after you create the 3.1.5 release, we can do an additional merge of 3.1.x into 3.2.x and create a 3.2.0 release.

Having at least a dev release of 3.2.x that's compatible with Drupal 11 would allow anyone wanting to try out the events_registration recipe to use composer to pull in a compatible version.

I'll hold off merging in the changes here to make sure you're good with this, however.

I am good with it, please proceed. When merging please edit the commit message so it reads Issue #3465606: Make compatible with Drupal 11 that helps people reviewing the commit log, thanks!

Done!

Added credit - should have 3.2.0 release out within a few days

New release: https://www.drupal.org/project/registration/releases/3.2.0 →

Automatically closed - issue fixed for 2 weeks with no activity.

There were some errors in the 3.2.x branch (my fault) so Drupal 11 support is now available here:
https://www.drupal.org/project/registration/releases/3.3.0 →
Use 3.3.x branch going forward.