Implement FabAuthManager.refresh_user for sliding JWT refresh

providers/fab/src/airflow/providers/fab/auth_manager/fab_auth_manager.py

@@ -315,6 +315,11 @@ def _fetch_user() -> User:
     def serialize_user(self, user: User) -> dict[str, Any]:
         return {"sub": str(user.id)}
 
+    def refresh_user(self, *, user: User) -> User | None:
+        if not user or user.is_anonymous:
+            return None
+        return user
+
     def is_logged_in(self) -> bool:
         """Return whether the user is logged in."""
         user = self.get_user()

providers/fab/tests/unit/fab/auth_manager/test_fab_auth_manager.py

@@ -246,6 +246,19 @@ def test_serialize_user(self, flask_app, auth_manager_with_appbuilder):
         result = auth_manager_with_appbuilder.serialize_user(user)
         assert result == {"sub": str(user.id)}
 
+    def test_refresh_user_returns_user_for_authenticated(self, auth_manager_with_appbuilder):
+        user = Mock()
+        user.is_anonymous = False
+        assert auth_manager_with_appbuilder.refresh_user(user=user) is user
+
+    def test_refresh_user_returns_none_for_anonymous(self, auth_manager_with_appbuilder):
+        user = Mock()
+        user.is_anonymous = True
+        assert auth_manager_with_appbuilder.refresh_user(user=user) is None
+
+    def test_refresh_user_returns_none_for_no_user(self, auth_manager_with_appbuilder):
+        assert auth_manager_with_appbuilder.refresh_user(user=None) is None
+
     @mock.patch.object(FabAuthManager, "get_user")
     def test_is_logged_in(self, mock_get_user, auth_manager_with_appbuilder):
         user = Mock()