Upload a porting document

Upload ONE porting document and get back its documentId. For the signed LOA / carrier invoice the id goes to loaDocumentId / invoiceDocumentId; for a country-specific document requirement (international ports) it becomes that requirement's fieldValue. Requirement documents are normalized to PDF automatically (regulators reject raw images). PDF, JPEG, or PNG, 10MB max. Uploads must be attached to an order within 30 minutes or the carrier deletes them.