feat(mean_field): added initial implementation

note this implementation lacks many tests

libmeanfield/interface/boundary/context.cppm

@@ -0,0 +1,34 @@
+module;
+#include "mean_field.h"
+
+export module mean_field:boundary.contexts;
+
+export namespace mean_field::boundary {
+    struct BoundaryContext {
+      mfem::Array<int> inf_bounds;
+      mfem::Array<int> stellar_bounds;
+    };
+
+    enum class Boundaries : uint8_t {
+        STELLAR_SURFACE = 1,
+        INF_SURFACE = 2
+    };
+
+    int operator-(
+        Boundaries b,
+        const int a
+    ) {
+        return static_cast<int>(static_cast<uint8_t>(b) - static_cast<uint8_t>(a));
+    }
+
+    struct Bounds {
+        double r_star_ref;
+        double r_inf_ref;
+    };
+
+    enum BoundsError : uint8_t {
+        CANNOT_FIND_VACUUM
+    };
+
+
+}