Add specialiced active cell subgrids

ApplicationLibCode/ReservoirDataModel/RigActiveCellLocalGrid.h

@@ -0,0 +1,36 @@
+/////////////////////////////////////////////////////////////////////////////////
+//
+//  Copyright (C) 2024 Equinor ASA
+//
+//  ResInsight is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  ResInsight is distributed in the hope that it will be useful, but WITHOUT ANY
+//  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+//  FITNESS FOR A PARTICULAR PURPOSE.
+//
+//  See the GNU General Public License at <http://www.gnu.org/licenses/gpl.html>
+//  for more details.
+//
+/////////////////////////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include "RigLocalGrid.h"
+
+class RigActiveCellGrid;
+
+class RigActiveCellLocalGrid : public RigLocalGrid
+{
+public:
+    explicit RigActiveCellLocalGrid( RigActiveCellGrid* mainGrid );
+    ~RigActiveCellLocalGrid() override;
+
+    RigCell&       cell( size_t gridLocalCellIndex ) override;
+    const RigCell& cell( size_t gridLocalCellIndex ) const override;
+
+private:
+    RigActiveCellGrid* m_mainActiveGrid;
+};