feat: add domain model foundation

tests/core/boundary_condition_test.cpp

@@ -0,0 +1,25 @@
+#include "fesa/core/BoundaryCondition.hpp"
+
+namespace {
+
+int require(bool condition) {
+    return condition ? 0 : 1;
+}
+
+} // namespace
+
+int run_boundary_condition_tests() {
+    const fesa::core::BoundaryCondition condition{1, fesa::core::Dof::UR3, 0.25};
+
+    if (const int result = require(condition.nodeId() == 1); result != 0) {
+        return result;
+    }
+    if (const int result = require(condition.dof() == fesa::core::Dof::UR3); result != 0) {
+        return result;
+    }
+    if (const int result = require(condition.value() == 0.25); result != 0) {
+        return result;
+    }
+
+    return 0;
+}