extractTimeStamp method
Returns the Unix timestamp for the token.
The caller can then decide if the token is about to expire and,
for example, issue a new token.
Implementation
int extractTimeStamp(final dynamic token) {
final (int timestamp, Uint8List data) = Fernet._getUnverifiedTokenData(
token,
);
// Verify the token was not tampered with.
_verifySignature(data);
return timestamp;
}