Remove Legacy Studio UI Waffle Flags and course_waffle_flags API endpoint

[farhan]

Summary

With the React-based Studio MFE (frontend-app-authoring) now fully handling all Studio pages, the LEGACY_STUDIO_* waffle flags and the API endpoint that served them can be removed from openedx-platform.

Parent epic: (link TBD — openedx/public-engineering)
Frontend sub-task: openedx/frontend-app-authoring#3063

Background

The GET /api/contentstore/v1/course_waffle_flags endpoint was added so the MFE could fetch server-side waffle flag state and conditionally route users to either the new React pages or the legacy Django-rendered Studio pages. That conditional routing is being removed on the frontend side; once shipped, this endpoint will receive zero traffic.

Implementation Details

1. Remove the API endpoint

File: cms/djangoapps/contentstore/rest_api/v1/urls.py

• Remove the URL pattern for course_waffle_flags

File: cms/djangoapps/contentstore/rest_api/v1/views/course_waffle_flags.py (or equivalent)

• Delete the view class/function

File: cms/djangoapps/contentstore/rest_api/v1/serializers/ (if applicable)

• Delete the CourseWaffleFlagsSerializer or equivalent

2. Remove waffle flag definitions

File: cms/djangoapps/contentstore/toggles.py

• Delete LEGACY_STUDIO_* flag constants (e.g., LEGACY_STUDIO_UNIT_PAGE, LEGACY_STUDIO_COURSE_OUTLINE_PAGE, etc.)
• Delete helper functions: use_new_unit_page(), use_new_course_outline_page(), use_new_home_page(), use_new_updates_page(), use_new_files_uploads_page(), use_new_video_uploads_page(), use_new_certificates_page(), use_new_textbooks_page(), use_new_custom_pages(), use_new_import_page(), use_new_export_page(), use_new_pdf_editor()

3. Clean up callers

Search for all call sites of the removed helper functions and remove them:

• cms/djangoapps/contentstore/utils.py — likely has URL-generation helpers conditioned on these flags
• cms/djangoapps/contentstore/views/component.py — may gate redirect logic on use_new_unit_page()
• Any remaining Django views that conditionally render legacy templates vs. redirect to MFE

4. Update tests

• Delete tests that specifically exercise the legacy routing paths (they test dead code)
• Remove override_waffle_flag / @override_waffle_switch decorators that set these flags in test setup
• Update API tests to expect 404 on the removed endpoint

5. OEP-0058 / Toggles annotation cleanup

If any of these flags are listed in cms/djangoapps/contentstore/toggles.rst or annotated via code_owner / toggle_name, remove those entries.

Flags Being Removed

Python helper	Waffle flag name
use_new_home_page()	contentstore.new_studio_mfe.use_new_home_page
use_new_course_outline_page()	contentstore.new_studio_mfe.use_new_course_outline_page
use_new_unit_page()	contentstore.new_studio_mfe.use_new_unit_page
use_new_updates_page()	contentstore.new_studio_mfe.use_new_updates_page
use_new_files_uploads_page()	contentstore.new_studio_mfe.use_new_files_uploads_page
use_new_video_uploads_page()	contentstore.new_studio_mfe.use_new_video_uploads_page
use_new_certificates_page()	contentstore.new_studio_mfe.use_new_certificates_page
use_new_textbooks_page()	contentstore.new_studio_mfe.use_new_textbooks_page
use_new_custom_pages()	contentstore.new_studio_mfe.use_new_custom_pages
use_new_import_page()	contentstore.new_studio_mfe.use_new_import_page
use_new_export_page()	contentstore.new_studio_mfe.use_new_export_page
use_new_pdf_editor()	contentstore.new_studio_mfe.use_new_pdf_editor

Acceptance Criteria

• GET /api/contentstore/v1/course_waffle_flags returns 404
• All LEGACY_STUDIO_* toggle constants are removed from toggles.py
• All helper functions (use_new_unit_page(), etc.) are deleted with no remaining callers
• All Studio pages continue to redirect to the MFE correctly (no legacy Django template fallback)
• CMS test suite passes with no flag-override test scaffolding for these flags