add msg.ToString()

include/sp/protocol/message/MessageInterfacesImpl.h

@@ -129,5 +129,17 @@ class MessageInterfaceWriteIdBase : public TBase {
 	}
 };
 
+// Debug print functionality chunk
+template <typename TBase>
+class MessageInterfaceToStringBase : public TBase {
+  public:
+	std::string ToString() const {
+		return ToStringImpl();
+	}
+
+  protected:
+	virtual std::string ToStringImpl() const = 0;
+};
+
 }  // namespace details
 }  // namespace sp