feat!: Package and Entity keys are now opaque refs

[kdmccormick]

Description

The {LearningPackage,PublishableEntity}.key fields were always meant to be externally-supplied refs whose format does not matter. However, they were effectively being used as parseable psuedo-keys for identifying containers and components, with more assumptions to their structure being baked in over time, both within and outside openedx-core.

This commit renames them to {package,entity}_ref, and removes all parsing of them from the API and from the internals (except for where required for backcompat with Ulmo ZIP backups). Instead, the pairings of (component_type,component_code) and (container_type,container_code) are used to identify components and containers; their respective entity_refs are derived from those by convention but the publishing app has no conception of this convention.

BREAKING CHANGES to openedx_django_lib:

• Renamed key_field(...) -> ref_field(...) in openedx_django_lib.

BREAKING CHANGES to models API:

• Renamed field LearningPackage.key -> LearningPackage.package_ref.
• Renamed field PublishableEntity.key -> PublishableEntityKey.entity_ref
• Renamed field PublishableEntityMixin.key -> PublishableEntityMixin.entity_ref
• Renamed property PublishableEntityVersion.key -> PublishableEntityVersion.entity_ref

BREAKING CHANGES to publishing API:

• In create_learning_package(...), renamed param key -> package_ref
• In update_learning_package(...), renamed param key -> package_ref
• In learning_package_exists(...), renamed param key -> package_ref
• In create_publishable_entity(...), renamed param key -> entity_ref
• Renamed get_publishable_entity_by_key(...) -> get_publishable_entity_by_ref(...), and renamed param key -> entity_ref
• Renamed get_learning_package_by_key(...) -> get_learning_package_by_ref(...), and renamed param key -> package_ref

BREAKING CHANGES to components APIs:

• Removed function get_or_create_component_type_by_entity_key()

BREAKING CHANGES to container APIs:

• Renamed get_container_by_key(...) -> get_container_by_code(...), and renamed param key -> container_code
• Rename get_container_children_entities_keys(...) -> get_container_children_entity_refs(...)
• Renamed get_container_children_entities_keys(...) -> get_container_children_entity_refs(...)

BREAKING CHANGES to collections API:

• In get_entity_collections(...), renamed param entity_key -> entity_ref

BREAKING CHANGES to media API:

• In look_up_component_version_media(...):
  • Renamed param learning_package_key -> learning_package_ref
  • Renamed param component_key -> entity_ref
• In add_assets_to_component management command:
  • Renamed argument learning_package_key -> learning_package_ref
  • Renamed argument component_key -> entity_ref

BREAKING CHANGES to backup_restore API:

• BREAKING CHANGE In load_learning_package:
  • Renamed param key -> package_ref
  • In return dict, within sub-dict ["lp_restored_data"]:
    • Renamed ["key"] -> ["package_ref"]
    • Renamed ["archive_lp_key"] -> ["archive_package_ref"]
    • Renamed ["archive_org_key"] -> ["archive_org_code"]
    • Renamed ["archive_slug"] -> ["archive_package_code"]
  • If archive_package_ref cannot be parsed into "{_prefix}:{org_code}:{package_code}", then archvie_org_code and archive_package_code will both be None. Callers should handle this case. (Previously, a ValueError would be raised by backup-restore code.)

Backup-restore still write and reads entity_ref and package_ref to/from TOML files as key
for backwards compatibility. This may change in a future "v2" restore format.

Part of: #322

Full series of PRs:

1. feat!: Collection.key -> Collection.collection_code #542
2. feat!: Component.local_key -> Component.component_code #544
3. feat!: Add Container.container_code field #545
4. feat!: Package and Entity keys are now opaque refs #546
5. feat!: ComponentVersionMedia.key -> ComponentVersionMedia.path #547

Testing, AI Usage, and Merge Considerations

See #322

[kdmccormick]

This is almost ready, but I'm still wrestling with translation between the backup-restore terms (keys) and the model terms (refs).

EDIT: It's all ready now.

[bradenmacdonald]

I read through the code and it looks great. Some very minor suggestions.
I did not test anything, but can do so when the platform PR is ready if you'd like.