Required. Barcode format. For the barcode dictionary, you can use only the following values:
PKBarcodeFormatQR, PKBarcodeFormatPDF417, or PKBarcodeFormatAztec.
For dictionaries in the barcodes array, you may also use PKBarcodeFormatCode128.
Required. Text encoding that is used to convert the message from the string representation
to a data representation to render the barcode. The value is typically iso-8859-1, but you may
use another encoding that is supported by your barcode scanning infrastructure.