Improvements to grouping deletion handling

[david-yz-liu]

Proposed Changes

(Describe your changes here. Also describe the motivation for your changes: what problem do they solve, or how do they improve the application or codebase? If this pull request fixes an open issue, use a keyword to link this pull request to the issue.)

This PR makes the following changes to grouping deletion:

• Prevent Grouping objects from being destroyed when they have associated submission at the model level (adding a dependent: :restrict_with_error option to the submissions association)
• In GroupsController#remove_group for handling instructor bulk deletion, ensure only groupings associated with the current assignment are deleted
• Removed redundant/dead code on instructor and student destroy grouping actions

Screenshots of your changes (if applicable)

Type of Change

(Write an X or a brief description next to the type or types that best describe your changes.)

Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)	X
🎨 User interface change (change to user interface; provide screenshots)
♻️ Refactoring (internal change to codebase, without changing functionality)	X
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
📖 Documentation update (change that updates documentation)
🔧 Internal (change that only affects developers or continuous integration)

Checklist

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Before opening your pull request:

• I have performed a self-review of my changes.
  • Check that all changed files included in this pull request are intentional changes.
  • Check that all changes are relevant to the purpose of this pull request, as described above.
• I have added tests for my changes, if applicable.
  • This is required for all bug fixes and new features.
• I have updated the project documentation, if applicable.
  • This is required for new features.
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• I have updated the project Changelog (this is required for all changes).
• I have verified that the pre-commit.ci checks have passed.
• I have verified that the CI tests have passed.
• I have reviewed the test coverage changes reported by Coveralls.
• I have requested a review from a project maintainer.

Questions and Comments

(Include any questions or comments you have regarding your changes.)

[coveralls]

Coverage Report for CI Build 32580006439

Coverage increased (+0.01%) to 90.684%

Details

• Coverage increased (+0.01%) from the base build.
• Patch coverage: 82 of 82 lines across 4 files are fully covered (100%).
• 4 coverage regressions across 1 file.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

4 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
app/controllers/groups_controller.rb	4	86.18%

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Coverage Stats

Relevant Lines:	52010
Covered Lines:	48187
Line Coverage:	92.65%
Relevant Branches:	2497
Covered Branches:	1242
Branch Coverage:	49.74%
Branches in Coverage %:	Yes
Coverage Strength:	129.51 hits per line

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💛 - Coveralls