chore: import upstream snapshot with attribution

backend/tests/test_user_session.py

@@ -0,0 +1,14 @@
+async def test_user_session_set_get(mock_chainlit_context, user_session):
+    async with mock_chainlit_context as context:
+        # Test setting a value
+        user_session.set("test_key", "test_value")
+
+        # Test getting the value
+        assert user_session.get("test_key") == "test_value"
+
+        # Test getting a default value for a non-existent key
+        assert user_session.get("non_existent_key", "default") == "default"
+
+        # Test getting session-related values
+        assert user_session.get("id") == context.session.id
+        assert user_session.get("env") == context.session.user_env