Protocol buffer definitions for custom xapps with OAI support.
The protocol is based on request-response transactions. Any request or response is identified by a RAN_message_type found in enum.proto. Requests and responses are not to be exchanged directly. They are instead encoded as submessages in RAN_message, whose fields contain the submessage ID and the payload. This way, every received protobuf message can always be unambiguously decoded as a RAN_message and then the submessage type can be inferred by the ID.