refactor: extract core domain dof modules

include/fesa/Property/Property.hpp

@@ -1,9 +1,22 @@
 #pragma once
 
+#include "fesa/Core/Types.hpp"
 #include "fesa/ModuleInfo.hpp"
 
+#include <string>
+
 namespace fesa::module {
 
 inline constexpr std::string_view kProperty = "Property";
 
 }  // namespace fesa::module
+
+namespace fesa {
+
+struct ShellSection {
+  std::string element_set;
+  std::string material;
+  Real thickness = 0.0;
+};
+
+}  // namespace fesa