Bulk-enroll a collection of contacts into course sections. Pass course_ids to enroll in every section of those courses, or section_ids for specific sections (or both). The action runs asynchronously — poll the returned record with GET /api/v2/contacts/enroll_actions/{id} to track progress via target_count and performed_count.
Exactly one target selection must be supplied: stable_id, stored_filter_id (alias filter_id), target_ids, or target_all. Returns 422 if none is provided or if the supplied value is invalid.