feat(poly): lagrangian constrained weak form of 3D lane-Emden

added a basic implimentation of the 3D lane emden equation using a lagrangian multiplier to constrain the value at the center of a spherical domain

src/poly/utils/public/polyMFEMUtils.h

@@ -1,3 +1,6 @@
+#ifndef POLYMFEMUTILS_H
+#define POLYMFEMUTILS_H
+
 #include "mfem.hpp"
 #include <string>
 
@@ -183,10 +186,10 @@ namespace polyMFEMUtils {
 
   class AugmentedOperator : public mfem::Operator {
     private:
-      std::unique_ptr<mfem::NonlinearForm> nfl;
-      std::unique_ptr<mfem::LinearForm> C;
+      mfem::NonlinearForm &nfl;
+      mfem::LinearForm &C;
       int lambdaDofOffset;
-      mfem::SparseMatrix *lastJacobian = nullptr;
+      mutable mfem::SparseMatrix *lastJacobian = nullptr;
 
     public:
       AugmentedOperator(mfem::NonlinearForm &nfl_, mfem::LinearForm &C_, int lambdaDofOffset_);
@@ -196,4 +199,6 @@ namespace polyMFEMUtils {
 
       virtual mfem::Operator &GetGradient(const mfem::Vector &x) const override;
   };
-} // namespace polyMFEMUtils
+} // namespace polyMFEMUtils
+
+#endif // POLYMFEMUTILS_H