Defining a source plugin type in a migration_group is broken in Drupal 10.3

I have updated the test files since there were not the correct ones.

The merge request solves the issue implementing hook_module_implements_alter, and making sure the migration_plugins_alter hook from migration_plus executes before anything else. This way, when the core action module executes its migration_plugins_alter hook, the migration configuration will already include the merged shared_confguration from the group.

Setting the issue as needs review.

Thanks for the fix here.

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