Compute well productivity index and pass it to the output

opm/autodiff/WellInterface.hpp

@@ -333,6 +333,8 @@ namespace Opm
 
         void solveWellForTesting(Simulator& ebosSimulator, WellState& well_state, const std::vector<double>& B_avg, bool terminal_output);
 
+        void scaleProductivityIndex(const int perfIdx, double& productivity_index) const;
+
     };
 
 }