Previously, Lightning Core provided a way to run updates that were "optional" -- changes that you could make, but didn't have to. This was wrapped up by a drush update:lightning command. This was originally written to keep sites that used the Lightning distribution up-to-date with upstream changes without breaking existing functionality.
Since the Lightning distribution is now end-of-life, this kind of update is no longer very useful, and it makes more sense to stop doing it. Other Lightning modules will no longer be providing optional updates (or, if at all possible, any kind of database or config update), so the optional update system is removed from Lightning Core 6.
The following classes are gone:
- \Drupal\lightning_core\UpdateManager
- \Drupal\lightning_core\UpdateTask
- \Drupal\lightning_core\Annotation\Update
- \Drupal\lightning_core\ComponentDiscovery
..as is the lightning.update_manager service.
Additionally, the phpdocumentor/reflection-docblock package, currently required by Lightning Core's composer.json, is no longer required. If you are actively using this package, you'll want to add it to your project's composer.json. For example: composer require phpdocumentor/reflection-docblock:^5.
