Deprecate the waffle-flag-states endpoint once authz.enable_course_authoring is removed

[mariajgrimaldi]

Description

GET /api/authz/v1/waffle-flag-states/ (added in #358, backed by openedx_authz.utils.get_waffle_flag_states()) exists only to expose the state of the authz.enable_course_authoring waffle flag to the admin-console MFE, so it can apply the "show if any tier is on, hide if all are off" rule from #340 and #341.

That flag is a temporary migration flag:

• toggle_target_removal_date: 2027-06-09
• Tracked upstream at Task - RBAC AuthZ - Implement feature flag for AuthZ for course authoring openedx-platform#37927

Once the flag is fully rolled out and removed from edx-platform, this endpoint (and the org/course override models it queries) will have no reason to exist. The admin-console MFE's dependency on it will also need to be removed at the same time.

Per ADR 0016, this endpoint is a bounded, documented exception to Authorization's domain ownership rule, not a pattern to repeat; this issue exists so that exception has a scheduled end.

Definition of Done

• authz.enable_course_authoring has been fully rolled out and removed from edx-platform
• GET /api/authz/v1/waffle-flag-states/, openedx_authz.utils.get_waffle_flag_states(), and the WaffleFlagStatesAPIView are removed from openedx-authz
• The admin-console MFE's usage of this endpoint is removed in the same window
• ADR 0015 (docs/decisions/0015-expose-course-authoring-waffle-flag-state-via-rest-api.rst) is updated to reflect the removal

References

• feat: add waffle flag states rest api and util #358 (introduced the endpoint)
• [Bug] Authoring-related UI is visible in lists when the waffle flag is off #340, [Bug] Hide Authoring roles in the role assignment wizard when Authoring is disabled at platform, org, and course level #341 (the MFE visibility rules this endpoint supports)
• ADR 0015: docs/decisions/0015-expose-course-authoring-waffle-flag-state-via-rest-api.rst
• ADR 0016: docs/decisions/0016-rest-api-domain-ownership-boundary.rst
• Task - RBAC AuthZ - Implement feature flag for AuthZ for course authoring openedx-platform#37927 (upstream flag removal tracking)