update change_due_date to DRF

[awais786]

Verify via postman

1: Use this URL
2: Role permissions ( course-roles as staff )
3: Add a graded unit via studio.

form-data

student =admin
url =block-v1:edx+cs222+23111+type@sequential+block@14a256f0a4e44466978ec41fca103710
due_datetime=08/30/2025
reason=testing ( this is optional param )

exptected result
"Successfully changed due date for student aaaa for Subsection (block-v1:edx+cs222+23111+type@sequential+block@14a256f0a4e44466978ec41fca103710) to 2026-08-30 00:00"

Verify via instructor dashboard.

You can verify the results form Viewing granted extensions section.