feat(partition-functions): added framework and some concrete partition functions

GroundState partition function, Rauscher&Thielemann partition function, and composite partition function added

src/network/include/gridfire/partition/partition_ground.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include "gridfire/partition/partition_abstract.h"
+
+#include "fourdst/logging/logging.h"
+
+#include <unordered_map>
+
+#include "quill/Logger.h"
+
+namespace gridfire::partition {
+    class GroundStatePartitionFunction final : public PartitionFunction {
+    public:
+        GroundStatePartitionFunction();
+        double evaluate(
+            const int z,
+            const int a,
+            const double T9
+        ) const override;
+        double evaluateDerivative(
+            const int z,
+            const int a,
+            const double T9
+        ) const override;
+        bool supports(
+            const int z,
+            const int a
+        ) const override;
+        std::string type() const override { return "GroundState"; }
+    private:
+        quill::Logger* m_logger = fourdst::logging::LogManager::getInstance().getLogger("log");
+        std::unordered_map<int, double> m_ground_state_spin;
+        static constexpr int make_key(
+            const int z,
+        const int a);
+    };
+
+}