Disable unenroll option for paid course

[Waleed-Mujahid]

Description

Paid courses unenrollment shows refund text currently and when user tries to enroll again it gives error saying "already enrolled". This PR updates the flow the disallow users from unenrolling from paid courses

Jira

https://edlyio.atlassian.net/browse/EDLY-7231

[manan-memon]

Can't we use any other endpoint to retrieve this information? Why do we need to create a new one?

[Waleed-Mujahid]

Can't we use any other endpoint to retrieve this information? Why do we need to create a new one?

@manan-memon The endpoint previously being used was course_run_refund_status but that one also returns based on if the refund expiry date has passed and give appropriate response if user can no longer refund the course. This API simplifies the logic of course_run_refund_status and only checks if user has paid for a course and returns true. There is no other to link a payment to a user and course