feat(redwood): implement optional completion

[Agrendalath]

This adds a new XBlock field that allows marking sections, subsections, and units as optional, so their completion is counted separately.

Note: I would suggest reviewing each commit individually here.

Testing instructions

1. Run pip install -e . in the edx-platform directory to rebuild Open_edX.egg-info.
2. Run tutor dev exec cms npm run build-dev.
3. Use feat(redwood): implement optional completion frontend-app-learning#88 for the Learning MFE.
4. Set the "Optional" completion for a section, subsection, and unit in the legacy Studio experience.
5. Check that each of these optional blocks has an "OPTIONAL" badge on the Course Outline page and in the Course Sidebar (in the courseware) within the Learning MFE.
6. Check that an optional unit has an alert (explaining that the completion is optional) above its rendered content.
7. Check that the optional completion is displayed on the Progress page.
8. Go to http://local.openedx.io:8000/admin/lms_xblock/xblockasidesconfig/add/ and press "Save".
9. Mark an individual XBlock as optional. Publish it. See the "OPTIONAL" badge above the XBlock's display name.
10. Check this individual XBlock in the Learning MFE.

Author's notes

Individual XBlock banners will be updated - we will leave only one, with an appropriate message. We probably won't use asides - this part is just a proof of concept.

Private-ref: BB-9331

[Agrendalath]

@tecoholic, I reverted the PoC for displaying individual XBlock completion. I will look into adding the final version next week. Please feel free to review the rest.

[tecoholic]

@Agrendalath 👍

• I tested this: Verified that the optional completion features work as mentioned in the PR testing instructions
• I read through the code
• I checked for accessibility issues
• Includes documentation

[tecoholic]

@Agrendalath This is a smart refactor :)

[tecoholic]

Wouldn't getattr(block, 'optional_completion', False) here return the same as is_explicitly_optional? Why not use the same value?

[Agrendalath]

@tecoholic, the optional_completion field comes from the InheritanceMixin, so it is true when any of the XBlock's parents had set it to true. By checking the explicitly set field, we ensure that the optional_completion has been set for this specific (individual) XBlock. We already display the optional banner when the unit is optional, so this information would be duplicated for each XBlock within this unit. Therefore, we want to show it only for optional XBlocks within a non-optional unit.

[tecoholic]

@Agrendalath I just realized the "Optional 4" banner is not actually there.

Check this individual XBlock in the Learning MFE. It should have an additional "Optional 4" banner.

The 3 in Studio

And the same 3 appear in the Learning MFE as well

[Agrendalath]

@tecoholic, as mentioned in #823 (comment), I reverted these banners. Yesterday, I pushed a commit that reimplements the "Optional 1" banner as an "OPTIONAL" badge above the XBlock's name, but I forgot to update this part in the testing instructions. I'll update it now.

[Agrendalath]

Note for future reference (because I will squash the commits): a59c421 and 27f938e demonstrate the use of asides to display optional completion.