feat: add domain model foundation

include/fesa/core/LoadDefinition.hpp

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "fesa/core/ModelTypes.hpp"
+
+namespace fesa::core {
+
+class NodalLoadDefinition {
+public:
+    NodalLoadDefinition(NodeId node_id, Dof dof, double value);
+
+    NodeId nodeId() const noexcept;
+    Dof dof() const noexcept;
+    double value() const noexcept;
+
+private:
+    NodeId node_id_;
+    Dof dof_;
+    double value_;
+};
+
+} // namespace fesa::core