Add definitions for GeoModel I/O types

GeoModelIO/GeoModelDBManager/GeoModelDBManager/definitions.h

+// Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
+
+/*
+ * This header file provides global definitions used 
+ * in the I/O of GeoModel into and from an SQLite file. 
+ *
+ *  Author:     Riccardo Maria BIANCHI @ CERN
+ *  Created on: May, 2024
+ *
+ */
+
+
+#ifndef GEOMODELDBMANAGER_DEFINITIONS_H
+#define GEOMODELDBMANAGER_DEFINITIONS_H
+
+#include <vector>
+#include <variant>
+
+// define the data types used to retrieve and store data from the DB
+using DBRecordEntry = std::variant<int,long,float,double,std::string>;
+using DBRowEntry = std::vector<DBRecordEntry>;
+using DBRowsList = std::vector<DBRowEntry>;
+
+#endif
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