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 is the serialized reliable message data (matches format in ReliableMessage).
Returns a ReliableMessage instance if parsing succeeds, null otherwise.
Implementation
ReliableMessage? parseReliableMessage(Mapping msg);