Start user-engine implementation scaffold

tests/test_domain_models.py

@@ -0,0 +1,28 @@
+import unittest
+
+from user_engine.domain import (
+    AuthorizationDecision,
+    AuthorizationEffect,
+    CatalogLifecycle,
+)
+from user_engine.testing.fixtures import sample_catalog
+
+
+class DomainModelTests(unittest.TestCase):
+    def test_catalog_exposes_attribute_keys(self):
+        catalog = sample_catalog()
+
+        self.assertEqual(catalog.lifecycle, CatalogLifecycle.ACTIVE)
+        self.assertEqual(catalog.attribute_keys(), {"demo.display_density"})
+
+    def test_authorization_decision_allowed_property(self):
+        self.assertTrue(
+            AuthorizationDecision(effect=AuthorizationEffect.ALLOW).allowed
+        )
+        self.assertFalse(
+            AuthorizationDecision(effect=AuthorizationEffect.DENY).allowed
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()