generateIdentity method
Generate the identity string to pass along in the header with
current date time now
Implementation
String generateIdentity(DateTime now) {
String formattedDate = DateFormat('EEE, dd MMM yyyy HH:mm:ss').format(now);
String encoded = base64.encode(
utf8.encode('$publicKey%$sessionToken%$formattedDate%$accountNumber'));
return encoded;
}