Access: System, Admin, and ClientAdmin users only.

Request format is multipart/form-data with file field file.
Import is create-only (existing records are not updated/deleted).

Row processing is independent and partial:
invalid rows are marked and processing continues until 5 consecutive row errors are reached.

Missing End Date defaults to Start Date.
Missing Country defaults to US.

On success returns 200 with JSON summary.
On row-level validation errors returns 422 with JSON summary and annotated XLSX (multipart/mixed).
Rows already marked as Success and locked are skipped on re-import.