[Course Live] Saving an LTI 1.1 configuration returns HTTP 500 in Studio

Saving an LTI 1.1 configuration under Studio → Content → Pages & Resources → Live fails with:

We couldn't apply your changes.
Please check your entries and try again.

The underlying Studio APIs return HTTP 500.

Environment

• Open edX release line: master
• Site: master.openedx.io
• Course: course-v1:OpenedX+CS51+2026
• LTI version: LTI 1.1
• Observed: July 31, 2026

Steps to reproduce

1. Open a course in Studio.
2. Go to Content → Pages & Resources.
3. Open the Live settings.
4. Select a provider.
5. Enter the LTI 1.1 credentials and required configuration fields.
6. Select Save.

Expected behavior

The Course Live configuration is saved successfully.

Actual behavior

Studio displays:

We couldn't apply your changes.
Please check your entries and try again.

A browser HAR captured the following failures:

2026-07-31T11:24:57.415Z
PATCH /api/course_apps/v1/apps/course-v1:OpenedX+CS51+2026
HTTP 500

2026-07-31T11:25:16.542Z
POST /api/course_live/course/course-v1:OpenedX+CS51+2026/
HTTP 500

2026-07-31T11:25:32.918Z
POST /api/course_live/course/course-v1:OpenedX+CS51+2026/
HTTP 500

Start by reproducing the save flow in Studio using the listed course and LTI 1.1 settings, then inspect the handlers for PATCH /api/course_apps/v1/apps/{course_id} and POST /api/course_live/course/{course_id}/. Done means both APIs return success and Studio saves the Course Live configuration without displaying the HTTP 500 error.