feat: Add some GitHub Classroom API endpoints

[jferrl]

Summary

This PR implements some GitHub Classroom API endpoints support by adding three new methods to the ClassroomService and fixes a deprecation warning in the addOptions function.

Changes Made

✨ New Features

1. GetClassroom Method

• Purpose: Retrieves a specific GitHub Classroom by ID for administrators
• API Endpoint: GET /classrooms/{classroom_id}

2. ListClassrooms Method

• Purpose: Lists all GitHub Classrooms for the current user
• API Endpoint: GET /classrooms

3. ListClassroomAssignments Method

• Purpose: Lists all assignments for a specific GitHub Classroom
• API Endpoint: GET /classrooms/{classroom_id}/assignments

Refactor

4. Reflect.Ptr Deprecation Fix

• Issue: Updated addOptions function to use reflect.Pointer instead of deprecated reflect.Ptr
• Change: Replaced reflect.Ptr with reflect.Pointer in github/github.go
• Benefit: Ensures compatibility with newer Go versions and removes deprecation warnings

Issue: #3684

[gmlewis]

@jferri - just FYI - I lost write access to this repo and this may cause unexpected delays for which I apologize.
You can watch that other PR to check on the status.

[jferrl]

@jferri - just FYI - I lost write access to this repo and this may cause unexpected delays for which I apologize. You can watch that other PR to check on the status.

No worries! 😃

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.11%. Comparing base (ffc5df8) to head (863baf5).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
github/classroom.go	86.66%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@ Coverage Diff @@## master #3690 +/- ##
==========================================
- Coverage 91.12% 91.11% -0.02% 
==========================================
Files 187 187 Lines 16640 16684 +44 ==========================================
+ Hits 15164 15202 +38 - Misses 1291 1295 +4 - Partials 185 187 +2 

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[gmlewis]

Thank you, @jferrl!
Just a few tweaks, please, then we should be ready for a second LGTM+Approval from any other contributor to this repo before merging.

@stevehipwell and/or @alexandear - might you have time for a code review? Thank you!

[jferrl]

Thank you, @jferrl! Just a few tweaks, please, then we should be ready for a second LGTM+Approval from any other contributor to this repo before merging.

@stevehipwell and/or @alexandear - might you have time for a code review? Thank you!

@gmlewis changes done! 😃

[stevehipwell]

LGTM

[gmlewis]

Thank you, @jferrl and @stevehipwell!
LGTM.
Merging.

[gmlewis]

Fixes: #3684.