Request an invoice for the order using plugin.
documentType
Document type (for order requests): 1) Invoice, 2) Packing Slip, 3) Purchase order, 4) Pre-forma-invoice.
number
Invoice number, if not provided it will be generated.
orderId
ID of the order related to invoice.
refundId
ID of the refund related to the refund receipt.
Returns InvoiceRequest .
