Instructor Dashboard - Bulk email tab URL uses wrong MFE host and path in instructor dashboard v2 API

[brianjbuck-wgu]

Description

The v2 instructor dashboard API (/api/instructor/v2/courses/{course_id}) returns an incorrect URL for the bulk_email tab. It currently uses INSTRUCTOR_MICROFRONTEND_URL with the path /instructor/{course_key}/bulk_email, but bulk email is served by a separate Communications MFE.

Current (incorrect)
http://apps.local.openedx.io:8081/instructor/course-v1:OpenEdX+DemoX+DemoCourse/bulk_email
Expected
http://apps.local.openedx.io:1984/communications/courses/course-v1:OpenEdX+DemoX+DemoCourse/bulk_email

Fix

In lms/djangoapps/instructor/views/serializers_v2.py, line 142, the bulk email tab URL is built using mfe_base_url (which is INSTRUCTOR_MICROFRONTEND_URL) and the /instructor/ path pattern:

'url': f'{mfe_base_url}/instructor/{str(course_key)}/bulk_email'

It should instead use COMMUNICATIONS_MICROFRONTEND_URL (default port 1984 in devstack) with the /communications/courses/ path pattern:

'url': f'{communications_mfe_url}/communications/courses/{str(course_key)}/bulk_email'

Steps to Reproduce

1. Call GET /api/instructor/v2/courses/{course_id} as a staff user for a course with bulk email enabled.
2. Inspect the tabs array in the response.
3. The bulk_email tab url points to the instructor MFE instead of the communications MFE.