Fixed bugs with section-starter file group mapping across multiple assignments

[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.)

When configuring assignment starter files, instructors can assign sections different starter file groups. However, this functionality had two problems when doing this assignment across different assignments:

1. Assigning a section in one assignment caused the section to be unassigned from starter file groups for all other assignments.
2. (after fixing the above) the configuration page would load section-starter file group mappings for all assignments, not just the currently selected assignment.

This PR fixes both of those bugs.

Screenshots of your changes (if applicable)

Associated documentation repository pull request (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)
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

Checklist

(Complete each of the following items for your pull request. Indicate that you have completed an item by changing the [ ] into a [x] in the raw text, or by clicking on the checkbox in the rendered description on GitHub.)

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.
• If this is my first contribution, I have added myself to the list of contributors.

After opening your pull request:

• 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]

Pull Request Test Coverage Report for Build 15123818930

Details

• 37 of 38 (97.37%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.004%) to 91.922%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
app/controllers/assignments_controller.rb	5	6	83.33%

Totals
Change from base Build 14870512584:	0.004%
Covered Lines:	41871
Relevant Lines:	44866

---

💛 - Coveralls