Import historical payroll data from CSV

Imports historical or correction payroll data from a CSV file. The CSV should be generated using the template from the generate import endpoint, filled in with the appropriate values.

Send the CSV as a multipart/form-data request with the file in a field named import_file (a .csv file).

The payroll must be a historical or correction payroll in draft status.

On success, the pay stub line items are populated with the imported data. On failure, the error response format depends on the Accept header: text/csv returns the original CSV with an added validation column containing inline error messages, while application/json returns a standard JSON validation error response.