Course: add Delete operation to /api/courses/{id} (admin only)

[addow]

Summary

Adds DELETE /api/courses/{id} to the Course #[ApiResource], restricted to ROLE_ADMIN.

• Uses API Platform's built-in remove processor (EntityManager::remove() + flush)
• The database-level onDelete: CASCADE on resource_node_id handles cleanup of the linked ResourceNode
• Mirrors the pattern used by other destructive operations on Course (Patch) and Session (Delete)

Notes

CourseVoter::DELETE grants course teachers delete rights, which would be too permissive for a course-level delete. The explicit is_granted('ROLE_ADMIN') sidesteps the voter and restricts access correctly.

Physical files (e.g. course illustrations on disk) are not automatically removed on delete — this is a pre-existing limitation shared by the legacy CourseRepository::deleteCourse().

[addow]

Follow-up: filesystem and ResourceNode cleanup are not handled

After further investigation, I want to flag a limitation of this implementation before it is merged.

What happens when DELETE /api/courses/{id} is called:

API Platform's default remove processor calls EntityManager::remove($course) + flush(). This only deletes the course DB row. The following are not cleaned up:

Left behind	Root cause
resource_node row (and all child rows)	The FK is on course.resource_node_id → resource_node.id. onDelete: CASCADE means "delete course when resource_node is deleted" — not the reverse. AbstractResource only has cascade: ['persist'], not cascade: ['remove'], so Doctrine never schedules the ResourceNode for removal.
All resource_file rows	ResourceNode.resourceFiles has cascade: ['persist', 'remove'], but this only fires if the ResourceNode is explicitly removed via Doctrine — which it isn't.
Physical files in var/upload/resource/	VichUploader's RemoveListener only fires when a #[Vich\Uploadable] entity (ResourceFile) goes through Doctrine's preRemove. Since no ResourceFile is ever Doctrine-removed, no files are deleted from disk.

The correct approach would be a custom StateProcessor for the Delete operation that walks the ResourceNode tree, removes each ResourceFile via Doctrine (so VichUploader fires), and then removes the ResourceNode — before the Course row itself is deleted. IllustrationRepository::deleteIllustration() already demonstrates this pattern for the illustration sub-resource.

The commented-out node-walking code in CourseRepository::deleteCourse() appears to be a scar from a previously abandoned attempt at the same problem.

Options going forward:

1. Merge as-is with the understanding that orphaned files need manual cleanup (same behaviour as the legacy CourseRepository::deleteCourse())
2. Add a custom CourseDeleteProcessor that properly cleans up the ResourceNode hierarchy before deletion

Happy to implement option 2 if that is the preferred direction.