parseReliableMessage abstract method
Parses a serialized Map into a ReliableMessage instance.
Validates the structure (required fields: data, keys, signature) and converts raw values (e.g., Base64 string → TransportableData for signature) to proper types.
msg: Serialized reliable message data (matches format in ReliableMessage)
Returns: ReliableMessage instance if parsing succeeds, null otherwise
Implementation
ReliableMessage? parseReliableMessage(Mapping msg);