createEnvelope abstract method
Creates a custom message envelope with specified routing metadata.
Builds an Envelope from explicit sender/receiver/timestamp parameters, forming the header of a message (routing information).
@param sender - Mandatory ID of the message sender
@param receiver - Mandatory ID of the message receiver (user/group)
@param time - Optional timestamp (defaults to current time if null)
@return Custom Envelope instance with routing metadata
Implementation
Envelope createEnvelope({required ID sender, required ID receiver, DateTime? time});