feat: duplicate tags when duplicating a tagged XBlock.

[pomegranited]

Description

Updates the TaggedBlockMixin to add a studio_post_duplicate handler which copies the tags on the source_item to the duplicated block.

More information

Closes openedx/modular-learning#181

Depends on

• feat: paste tags when pasting xblocks with tag data [FC-0049] openedx/edx-platform#34270
• feat: add get_taxonomy_by_export_id method [FC-0049] openedx/openedx-learning#164

Private ref: FAL-3623

Testing instructions

1. Run this branch on your devstack, and ensure you've installed the branch from feat: add get_taxonomy_by_export_id method [FC-0049] openedx/openedx-learning#164 on LMS + CMS.
2. Enable and run the frontend-app-course-authoring MFE
3. Set up Taxonomy/Tags data setup locally using https://github.com/open-craft/taxonomy-sample-data/
4. Choose a unit from a course, and add several content tags from a few taxonomies.
5. Add a block to the unit, and add several content tags to that too.
6. Duplicate this tagged unit from the content outline using this button:
7. Ensure the new duplicate unit has the same tags as the source unit, and the duplicated child block also has the same tags as the source block.

Author Notes & Concerns

The implementation plan sketched out in openedx/modular-learning#181 has a flaw: When I tried storing the tag data in duplicate_metadata, eventually modulestore.create_item calls partition_fields_by_scope, which tries to call field = getattr(cls, 'tags-v1'). This errors out because tags-v1 isn't a real XBlock field.

We could fix this by refactoring TaggedBlockMixin to use a proper XBlock field for the tag data (and since we can't have a class attribute with a hyphen in it, we'd need to rename the field from tags-v1 to tags_v1).

Instead, I chose to use the XBlock studio_post_duplicate handler, as shown. A disadvantage of this approach is there's no good way to disable duplicating content tags when duplicating an XBlock; content tags will always be duplicated too.

[yusuf-musleh]

@pomegranited Looks good to me, thanks for taking this over! 👍

• I tested this: I tested duplicating units and blocks contains tags though both studio and the new mfe, and confirmed that the tags including children's tags have been duplicated
• I read through the code
• I checked for accessibility issues
• Includes documentation
• I made sure any change in configuration variables is reflected in the corresponding client's configuration-secure repository.

[pomegranited]

Hi @rpenido, I'd like to merge this into your open PR branch for openedx#34270. Is that ok with you?

Feel free to hit "Squash and Merge" when you're ready.

[rpenido]

Sure @pomegranited! Done!