feat: follow migrated legacy library content block

[navinkarkera]

Description

Allows authors to migrate legacy library content block in course to library v2 if the source library was migrated. The block works with the new library and has the same functionality as the new ItemBankBlock.

This PR also fixes some issues with Problem Bank like Add components button not working in the preview page and iframe postMessage failure after syncing of component in the preview page.

screencast.mp4

Requirements as per The LegacyLibraryContentBlock OLX must work forever.

• The LegacyLibraryContentBlock OLX must work forever.
• L points at a legacy library, which has been migrated to a new V2 library.
  • Block Behavior: Preview and settings editor should look just like a modern ItemBank block.
  • Child Behavior: If updates are available (see below), they are shown per-child on the View page, using the migrated child blocks as the update source.
• L points at a legacy library, which has not been migrated.
  • Block and Child Behavior: Use existing LegacyLibraryContentBlock interface behavior.
• L is None, malformed, or doesn't point to an existing or migrated legacy library:
  • Block Behavior: Display a validation error. Syncing is not allowed. (existing behavior)
  • Child Behavior: Children are displayed if they exist, but no option to sync is offered.
    Sync behavior
• The parent LegacyLibraryContentBlock's version does not equal the migrated source library version (indicating that the legacy library received updates before its migration happened)

Useful information to include:

• Which edX user roles will this change impact? "Course Author" and "Developer"

Supporting information

• Follow migrated LegacyLibraryContentBlock references frontend-app-authoring#2386
• Private-ref: https://tasks.opencraft.com/browse/FAL-4251
• Related PR: fix: add components button in item bank children page frontend-app-authoring#2491

Testing instructions

• Create a legacy library with some components.
• Add a legacy library content block in course unit.
• Now migrate the legacy library.
• Refresh the course unit page, a new alert should appear on top of the library content block.
• Click on migrate button in the alert and verify that the block is migrated to Problem bank and behaves like it.
• The children blocks have upstream field set and show sync button if the v2 library component is updated.

Deadline

"None" if there's no rush, or provide a specific date or event (and reason) if there is one.

Other information

Include anything else that will help reviewers and consumers understand the change.

• Does this change depend on other changes elsewhere?
• Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.
• If your database migration can't be rolled back easily.

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[kdmccormick]

@navinkarkera I'm not sure this is the best approach. The point of this method is to render the block, not to modify it--sticking the migration here is surprising and auto-magical. It will also update the children when the block is rendered in LMS, which would either fail or be a no-op, and would be confusing either way. In general, we should not be modifying content except in response to the action of a Studio user.

I had tried to outline an idea to follow library_content child references without a child migration process, but since writing that, I've also come to dislike the idea, because it would break the simplifying assumption that we can just check self.upstream on any block to see its upstream link. So, I like that your PR uses a migration child step, but I think we need some explicit way to trigger it.

Here's an idea:

• When a legacy library_content block has (a) unmigrated chidlren and (b) a migrated source library, it gives the users the option to "sync" the latest content, regardless of whether are new changes in the target library.
• Syncing, in this case, will migrate the children.

It's a slight product behavior change. In particular, every legacy library content block would have a "sync available" as soon as an operator migrates its source library. But, I think it would be worth the simplified behavior information architecture. What do you think?

[navinkarkera]

@kdmccormick This is not the final version, locally I have something like this:

Sorry for the confusion.

[navinkarkera]

Once the author clicks on Migrate it looks like this:

I'll update the PR description once I push the changes.

[kdmccormick]

Cool, thanks. I think this is a good approach. I'll ask precisely what the UI should be at the sync-up tomorrow.