feat: add methods for computing protocol version signature and retrieving version for packet type

src/NLPacketCodec.hpp

@@ -102,6 +102,10 @@ public:
     void setSequenceNumber(SequenceNumber seq);
     void setSourceID(LocalID id);
     
+    // Protocol version signature
+    static std::vector<uint8_t> computeProtocolVersionSignature();
+    static uint8_t versionForPacketType(PacketType type);
+    
 private:
     void writeHeader();