update list_background_email_tasks to DRF

[awais786]

existing code

Postman URL

{
  "tasks": [
    {
      "task_type": "bulk_course_email",
      "task_input": "{\"email_id\": 3, \"to_option\": [\"myself\"]}",
      "task_id": "22d37e27-976f-4de1-8c64-47218fadfce7",
      "requester": "admin",
      "task_state": "SUCCESS",
      "created": "2024-07-31T07:24:08.246044+00:00",
      "duration_sec": 0,
      "status": "Complete",
      "task_message": "Message successfully emailed for 1 recipients"
    },
    {
      "task_type": "bulk_course_email",
      "task_input": "{\"email_id\": 2, \"to_option\": [\"myself\"]}",
      "task_id": "37cd0989-aa6a-4503-8c7d-02abc478e6c7",
      "requester": "admin",
      "task_state": "SUCCESS",
      "created": "2024-07-31T07:20:30.308007+00:00",
      "duration_sec": 0,
      "status": "Complete",
      "task_message": "Message successfully emailed for 1 recipients"
    }
  ]
}

end to end testing

1. Go to instructor page and then email tabe here ( use your course id )
2. Click on To use the email tool, visit the new experience.
3. Click on show email task history