Add CSV export support to partner catalog list endpoints via DRF rend…

[ccantillo]

CSV Export via DRF Content Negotiation (?format=csv)

Summary

• Add CSV export capability to partner catalog list endpoints using DRF's content negotiation
• Clients request CSV by appending ?format=csv or sending Accept: text/csv header
• No new endpoints, dependencies, or serializer changes required

Endpoints affected

Endpoint	CSV filename
GET /partner_catalog/api/v1/manage/catalogs/?format=csv	catalogs_report.csv
GET /partner_catalog/api/v1/manage/catalogs/{pk}/learners/?format=csv	learners_report.csv
GET /partner_catalog/api/v1/manage/catalogs/{pk}/courses/?format=csv	courses_report.csv
GET /partner_catalog/api/v1/manage/catalogs/{pk}/enrollments/?format=csv	enrollments_report.csv
GET /partner_catalog/api/v1/manage/catalogs/{pk}/courses/{course_id}/enrollments/?format=csv	course_enrollments_report.csv

What changed

New files

• partner_catalog/helpers/renderers.py — Custom CSVReportRenderer (DRF BaseRenderer) that flattens nested serializer data using dot notation and writes CSV with human-readable headers.
• partner_catalog/helpers/mixins.py — CSVExportMixin that appends the CSV renderer, disables pagination for CSV responses, sets the Content-Disposition header, and works around Open edX's URL_FORMAT_OVERRIDE = None setting.

Modified files

• partner_catalog/api/v1/views.py — Added CSVExportMixin to PartnerCatalogViewSet, CatalogLearnerViewset, CatalogCourseViewSet, CatalogEnrollmentsViewSet, and CatalogCourseEnrollmentViewSet with per-viewset csv_fields, csv_labels, and csv_filename.

Test plan

• GET .../catalogs/?format=csv returns CSV with headers: Catalog Name, Slug, Status, Courses, Enrollments, Total Learners, Active Learners, Certified, Completion Rate, Available Start Date, Available End Date
• GET .../learners/?format=csv returns CSV with headers: Full Name, Email, Active, Invite Sent At, Accepted At, Last Login, Enrollments, Certified, Removed At
• GET .../courses/?format=csv returns CSV with headers: Course Name, Position, Start Date, End Date, Enrollment Start, Enrollment End, Enrollments, Certified, Completion Rate
• GET .../enrollments/?format=csv returns CSV with headers: Full Name, Email, Active, Last Login, Course Name, Course ID, Progress, Has Certificate
• GET .../courses/{course_id}/enrollments/?format=csv returns CSV with headers: Full Name, Email, Active, Last Login, Progress, Has Certificate
• Accept: text/csv header also triggers CSV download
• Existing filters and search work with ?format=csv (e.g. ?format=csv&search=john)
• Without ?format=csv, endpoints return JSON as before
• Response includes Content-Disposition: attachment; filename="<name>.csv" header
• Pagination is skipped for CSV (full dataset exported)

[Alec4r]

LGTM

[Alec4r]

@dcoa @bra-i-am could you help me updating the MFE with the endpoints to download these CSVs? Thanks.