feat: Make AuthenticatedData originator configurable with backward compatibility

[crStiv]

Previously the target_originator in AuthenticatedData was hardcoded to 100.
This change makes it configurable while maintaining backward compatibility:

• Adds optional originator parameter to AuthenticatedData::with_topic
• Maintains default value of 100 for backward compatibility
• Makes the API more flexible for future use cases
• Resolves TODO comment

The change is backward compatible and doesn't require updates to existing code.