generateSerialNumber abstract method
Generates a unique serial number (SN) for message content.
The SN serves as a unique message ID (uint64) to track and deduplicate messages.
msgType: Type of the message content (used for algorithm-specific generation)
now: Timestamp to incorporate into the SN (or current time if null)
Returns: 64-bit unsigned integer (uint64) as unique serial number
Implementation
int generateSerialNumber(String? msgType, DateTime? now);