Honor approver collapse preference in review email

[jhunterjActual]

Summary

• honor the assigned approver's collapsed compare-view preference in the “GCD change to review” email
• preserve the existing expanded link when that preference is disabled
• document that the compare route currently has no query parameters and must merge any future ones
• add regression coverage for both preference values

Testing

• pytest gcd-django/apps/oi/tests/test_views.py
• python manage.py check
• python -m flake8 apps/oi/views.py apps/oi/tests/test_views.py
• git diff --check
• mounted runtime health check returned HTTP 200

[gemini-code-assist]

Code Review

This pull request updates the submission email logic to respect the approver's preference for collapsing the compare view by appending ?collapse=1 to the comparison URL when enabled, and adds a corresponding test case. The review feedback suggests adding a defensive check to ensure the approver has an associated Indexer profile before accessing its attributes, preventing potential RelatedObjectDoesNotExist exceptions.