A card mask is a template for the format of a card number.
If the gift card number is longer than the default card mask, you will need to override this with your own mask.
For example, the default card mask is 9 digits and is formatted like "xxx-xxx-xxx".
To override the default card mask, specify the format in the cardMask parameter. For example, a 16 digit card number would be formatted like so: "xxxx-xxxx-xxxx-xxxx"