sourceId property
SourceID is the single-use payment token that stands in for the card: a Square Web Payments SDK nonce minted in the browser, or a Square sandbox test nonce when the org's credentials are sandbox ones. The card number itself never reaches this process, which is what keeps it out of PCI scope.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? sourceId;