fetchInvoice method generates and returns an Invoice, for the given invoiceId, as plain text or as a PDF. (It does not fetch a previously sent Invoice.)
Input
srd: sparse response description, a SOAP string (which must be a JSON object), in which you specify the elements you want returned.This parameter enables the calling system to constrain amethod call to return only components you specify. This gives you greater control over returned content, and improves response time within the Vindicia platform by reducing the processing needed for the call.
Some fields are required, either practically or in the WSDL, and will be returned regardless of the srd. A null srd returns the complete response.
autobill: the AutoBill for the requested invoice.
invoiceId: the ID of the invoice.
asPDF: a Boolean flag, which, if set to true, returns the object as a PDF. Default is false.
statementTemplateId: the Merchant Identifier for a pre-defined statement template. If null, the template defined by the AutoBill will be used. (Note that use of the forward slash character (/) in merchant identifiers is not allowed. See Merchant Identifiers for more information.)
dunningIndex: the index number of the requested invoice. (If the invoice was the first issued to the customer, its dunningIndex is 0.)
For more information, see Working with Invoices in the Subscribe Programming Guide.
language: the language of the invoice.
Output
return: an object of typeReturn that indicates the success or failure of the call.
invoice: the specified invoice, rendered as a PDF or as plain text. This field encodes both plain text and PDF as xsd:base64Binary.

