responseCode property
Response code. "0" means approved. null (status v2 only) means the
transaction is still in progress — see isInProgress. An empty string
from the terminal is normalised to null by fromJson: an empty code
carries no more information than a missing one, and treating it as a
real (non-"0") code would misreport an unresolved outcome as
declined.
Nicht jeder vorhandene Code ungleich "0" ist eine Ablehnung:
noStatementCode ist eine Wissensluecke, siehe isConclusive.
Implementation
final String? responseCode;