feat: Add ListAcceptedAssignments and GetAssignmentGrades methods to Classroom API

[jferrl]

Fixes: #3684.

Summary

This PR adds support for two missing GitHub Classroom API endpoints by implementing the ListAcceptedAssignments and GetAssignmentGrades methods in the ClassroomService.

Changes

New Methods

• ListAcceptedAssignments - Lists accepted assignments for a specific assignment
• GetAssignmentGrades - Retrieves assignment grades for a specific assignment

API Coverage

This completes the implementation of all 6 available GitHub Classroom API endpoints:

• ✅ GET /assignments/{assignment_id} → GetAssignment()
• ✅ GET /assignments/{assignment_id}/accepted_assignments → ListAcceptedAssignments() ← NEW
• ✅ GET /assignments/{assignment_id}/grades → GetAssignmentGrades() ← NEW
• ✅ GET /classrooms → ListClassrooms()
• ✅ GET /classrooms/{classroom_id} → GetClassroom()
• ✅ GET /classrooms/{classroom_id}/assignments → ListClassroomAssignments()

[jferrl]

@gmlewis this is the latest PR to close #3684 😃

[gmlewis]

Fixes: #3684.

[codecov]

Codecov Report

❌ Patch coverage is 91.42857% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.11%. Comparing base (1b53270) to head (9bce5fc).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
github/classroom.go	91.42%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3732      +/-   ##
==========================================
- Coverage   91.11%   91.11%   -0.01%     
==========================================
  Files         187      187              
  Lines       16686    16697      +11     
==========================================
+ Hits        15204    15213       +9     
- Misses       1295     1296       +1     
- Partials      187      188       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[gmlewis]

Thank you, @jferrl!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @alexandear

[alexandear]

Maybe it's better to create a separate struct ClassroomUser and use it instead of the User?

This struct will contain only 4 fields while the User has more than 20 fields:

          "title": "Simple Classroom User",
          "description": "A GitHub user simplified for Classroom.",
          "type": "object",
          "properties": {
            "id": {
              "type": "integer",
              "examples": [
                1
              ]
            },
            "login": {
              "type": "string",
              "examples": [
                "octocat"
              ]
            },
            "avatar_url": {
              "type": "string",
              "format": "uri",
              "examples": [
                "https://github.com/images/error/octocat_happy.gif"
              ]
            },
            "html_url": {
              "type": "string",
              "format": "uri",
              "examples": [
                "https://github.com/octocat"
              ]
            }
          },
          "required": [
            "id",
            "login",
            "avatar_url",
            "html_url"
          ]

[jferrl]

Done!

[alexandear]

Suggested change

	GithubUsername *string `json:"github_username,omitempty"`
	GitHubUsername *string `json:"github_username,omitempty"`

[gmlewis]

No, we decided years ago that in this repo, we are going to strictly follow the capitalization of the JSON tag, so that GithubUsername in this case is correct.

If they had named the field git_hub_username, then you would be right, but they don't, so we don't.

I'll see if I can find the conversation.

[gmlewis]

Here's one instance, but am still trying to find the original decision with the repo's original author.
#2851 (comment)

[gmlewis]

Maybe this is what I'm thinking of, although I'm pretty sure there was a separate discussion specifically about Github vs GitHub.
#605

[alexandear]

Can we improve also PR's title? The PR is definitely not a "chore" but a "feature".

[gmlewis]

Thank you, @alexandear!
Merging.