feat: improve Canvas grade sync and add test coverage

[xitij2000]

Description (What does it do?)

This PR enhances the Canvas grade synchronization functionality with improved validation logic and
comprehensive test coverage:

Key Changes:

1. Assignment Due Date Validation - Added a new validation check to prevent grade
   synchronization for assignments that have already passed their due date. When attempting to sync
   grades for an overdue assignment, the system will now log a warning and skip the synchronization.

2. Refactored Task Structure - Split the sync_user_grade_with_canvas shared task into two
   components:

   • sync_user_grade_with_canvas() - The Celery shared task decorator
   • _sync_user_grade_with_canvas() - The internal implementation function

   This separation improves testability and allows the implementation logic to be tested
   independently without Celery.

3. New Test Suite - Added a new test module (tests/test_tasks.py) with 8 test cases
   covering:

   • Successful grade synchronization
   • Missing Canvas course IDs
   • Assignments not present in Canvas
   • Past due date scenarios
   • Missing Canvas student IDs
   • Grade lookup failures
   • API response error handling

4. Test Configuration - Added pytest configuration:

   • conftest.py - Test setup with Django settings initialization for bulk email configuration
   • pyproject.toml pytest settings - Configured with database reuse and deprecation warning
     filters

How Can This Be Tested?

Unit Tests

Run the new test suite using the standard test process. Or you can mount this pacakge in the Tutor
openedx container, cd into the directory and run pytest.

Manual Testing

To manually test the functionality:

1. Create a grade record in Open edX for a Canvas-integrated course
2. Verify that grades for current assignments sync successfully with Canvas. You can do this through the shell:

      from ol_openedx_canvas_integration.tasks import _sync_user_grade_with_canvas
      from lms.djangoapps.grades.models import PersistentSubsectionGrade
      # Look up a grade record's id
      _sync_user_grade_with_canvas(grade_id)
        

3. Set an assignment's due date to the past in Canvas and trigger a grade sync - confirm it's skipped with a
   warning log

[tecoholic]

@xitij2000 I tested the changes with an actualy Canvas instance and Open edX instance. They work as expected and I can verify it from the logs as well.

I think we can improve the tests a bit and then it should be ready.

[tecoholic]

These settings are added in conftest.py for compatibility and are not actually used in any of the tested functionality, right? Do we need to override them here?

[xitij2000]

Nope, this is from before i added them to the test config.

[tecoholic]

Why is this not synced? It would be clear if the reason is in the test case name itself, or at least a docstring explaining it. From the test, it looks like canvas returns an assignment with no due date, which should ideally be syncing the grades. Why is it not?

[xitij2000]

I've updated the test. I too forgot why this shouldn't sync, so it definitely needs clarification!

[tecoholic]

Not really sure what's going on in this test. Test function name says, it's "sync error", the docstring says "test successful grade sync", finally it's asserted as "not called". What's this test actually checking?

I am guessing it's this block?

   try:
        grade = grade_dict[grade_instance.full_usage_key][openedx_user]
        payload = dict([update_grade_payload_kv(canvas_user_id, grade.percent_graded)])
    except (KeyError, AttributeError):

Can we make the docstring a bit more informative about why this condition occurs?

[xitij2000]

Sorry about that! I basically copied the success case and then started introducing failures to test all possible failures which left in docstring. I've updated this.

To be honest, I don't know why this would occur. This code is only run if the a grade is generated, so why would it not be returned from here, I'm not sure of the whole grading mechanism to know why we'd generate an object but still have the grading API not return a grade. If you know why this could happen, do tell and I'll update the docstring.