[MNG-1904] Fix: update new runtime's runtime.anonymous_student_id to store in DB

[bradenmacdonald]

This addresses a longstanding TODO item to make runtime.anonymous_student_id for content libraries v2 work the same way as it does for XBlocks in regular courses, persisting the anonymous ID string to the database. This way, if SECRET_KEY is changed, existing anonymous IDs will continue to work unchanged.

This is a potentially breaking change for XBlocks in these blockstore-based libraries (v2 libraries), because the actual anonymous_student_id values generated are now different (old ones were based on only user ID and secret key but didn't also incorporate the "context key" into the hash as the new IDs do). But based on my searching for anonymous_student_id in the codebase, this should only affect capa problems using external code graders or Matlab code input, and I'm not aware of any such usage of the new runtime / libraries v2.

Risks

There is a low risk that this change to anonymous_student_id causes issues for some LabXchange XBlocks (LabXchange being essentially the only user of the new runtime so far). Based on my code searching and manual testing, I don't believe anonymous_student_id is actually used meaningfully (they don't use external graders nor matlab input), so I don't expect any problems. However, if we wanted to be more conservative we could use a transition period where the existing IDs are stored into the table, before we change to the newer ID format

Database migration

It has one, but it doesn't make any changes (no SQL); it's just a change to the django model.

Testing

How I tested this change:

1. Used Ramshackle to create a v2 content library with a multiple choice capa problem. Published it, then using the "Learn" tab, submitted an answer.
2. Then I made these changes, and refreshed the page. I verified using debug logging that the anonymous_student_id for that problem+user did change, but the previously submitted answer was still selected.
3. I ran the integration tests for libraries v2 as described at https://github.com/edx/blockstore/#running-integration-tests - they mostly passed and there were no issues related to this PR; however, a few failed in the CMS test suite because [BD-19] Transition to the Elasticsearch 7.8.0 version edx-search#104 seems to have introduced a breaking change to edx-search and nobody has yet updated the libraries code accordingly. I've asked my team to look into that.

[openedx-webhooks]

Thanks for the pull request, @bradenmacdonald! I've created OSPR-5430 to keep track of it in JIRA.

As a core committer in this repo, you can merge this once the pull request is approved per the core committer reviewer requirements and according to the agreement with your edX Champion.

[bradenmacdonald]

@feanil Here's a PR for the issue we discussed on Slack.

[bradenmacdonald]

@pomegranited @symbolist Do you have any concerns about this change to runtime.anonymous_student_id for XBlocks on LabXchange?

[edx-status-bot]

Your PR has finished running tests. There were no failures.

[pomegranited]

@pomegranited @symbolist Do you have any concerns about this change to runtime.anonymous_student_id for XBlocks on LabXchange?

No concerns from me -- I agree with your assessment that LabXchange content doesn't use the anonymous_student_id. There's some content types in planning stages for LX which might need to use this identifier though, so it's great that you've fixed this now.

this should only affect capa problems using external code graders or Matlab code input

edx-ora2 submissions also use anonymous_student_id, but LX doesn't use them ORA2 either.

[feanil]

Looks good to me but I'm not as familiar with this part of the system so a review from @symbolist or @ormsbee would be great before I merge this.

[openedx-webhooks]

@bradenmacdonald 🎉 Your pull request was merged!

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[openedx-webhooks]

@ormsbee, @kdmccormick: thought you might like to know that bradenmacdonald merged this pull request.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.