CallDataSerializer

Bridges the user's wire-format T (a JSON string, a JNI Any? graph, etc.) to / from typed values. Implementations are tied to a specific wire format: a StringSerializer round-trips through kotlinx.serialization's string formats, a JniSerialization round-trips through the JNI Any? envelope, and so on.

Only successful payloads pass through this interface. Error responses are carried as the CallData.Error variant by the routing layer; transports encode and decode that variant natively (HTTP status codes, JSON-RPC error envelopes, packet error fields, etc.) and never round-trip an error through this serializer.