Add questionnaire reset functionality

[reppuli92]

Description

What?

Make questionnaire exercises reset and not show previous answer when they have been edited or when the course language is changed

Why?

This is done so that the correct version of a questionnaire is always shown to students

How?

A-plus checks an exercise version hash from mooc-grader (separate PR on mooc-grader) and compares it to the latest submission's hash. The page's language is compared as well to the submission's, and if either mismatch, the form is reset.

Fixes #494

Testing

Remember to add or update unit tests for new features and changes.

• How to test your changes in A-plus
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What type of test did you run?

• Accessibility test using the WAVE extension.
• Django unit tests.
• Playwright tests.
• Other test. (Add a description below)
• Manual testing.

I tested that the reset functionality works in the UI by editing aplus-manual and reloading a-plus while keeping old submission data cached. I also tested the language change.

Did you test the changes in

• Chrome
• Firefox
• This pull request cannot be tested in the browser.

Think of what is affected by these changes and could become broken

Translation

• Did you modify or add new strings in the user interface? (Read about how to create translation)

Programming style

• Did you follow our style guides?
• Did you use Python type hinting in all functions that you added or edited? (type hints for function parameters and return values)

Have you updated the README or other relevant documentation?

• documents inside the doc directory.
• README.md.
• Aplus Manual.
• Other documentation (mention below which documentation).

Is it Done?

• Reviewer has finished the code review
• After the review, the developer has made changes accordingly
• Customer/Teacher has accepted the implementation of the feature

Clean up your git commit history before submitting the pull request!

[Copilot]

Pull request overview

This PR adds “questionnaire reset” behavior by tracking an exercise content-version hash (from mooc-grader) and the submission language, and reloading a fresh exercise page when the latest submission no longer matches the current exercise version or UI language.

Changes:

• Persist an exercise_version hash from the exercise service into ExercisePage and ExerciseCache.
• Stamp the current exercise_version into new submissions’ metadata for later compatibility checks.
• In the exercise view, compare the latest submission’s stored version/language against the current ones and reset (reload blank exercise) on mismatch.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
exercise/views.py	Adds reset logic when current exercise version/language differs from the latest submission’s metadata.
exercise/submission_models.py	Stamps exercise_version into submission metadata at submission creation time.
exercise/protocol/exercise_page.py	Introduces exercise_version field on ExercisePage.
exercise/protocol/aplus.py	Parses x-aplus-exercise-version from the remote page meta into ExercisePage.
exercise/cache/exercise.py	Stores exercise_version in the cached exercise page data and refreshes legacy cache entries.

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[reppuli92]

Sorry for the confusion :) tried to make things look nice on my repo but ended up breaking things

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[ihalaij1]

Nice!

I tested this a bunch, found and fixed some bugs with the help of AI, but I would still want @murhum1 to go through this PR to increase the confidence that this doesn't cause any issues.

[murhum1]

Looks reasonable. What's the idea behind VERSION_MAX_AGE, though? If there's been no changes, why would we need to reload?

[ihalaij1]

I believe that was added by AI as a fallback in case the exercise somehow gets modified without triggering A+ exercise cache invalidation:

"VERSION_MAX_AGE prevents trusting that raw version hash forever. After 15 minutes, it returns “no cached version,” causing the view to load the exercise page and try to obtain a current hash.

• If all questionnaire edits reliably trigger A+ cache invalidation, VERSION_MAX_AGE is redundant.
• If upstream edits can bypass invalidation, the idea is necessary."

But in our case edits that save the A+ LearningObject already invalidate the cache and reset the exercise correctly without the age limit, so VERSION_MAX_AGE is probably unnecessary.

What do you think @murhum1 ?