fix(issuing): document is_single_use on update-card-response for virtual cards

Swagger 2026-09-23 split update-card-response into a virtual/physical
discriminator; the virtual variant adds is_single_use (specifies whether the
card is set to expire after a single use). Physical cards never send it. This
SDK has no typed issuing response classes, so this is a doc + test update.

Author: armando-rodriguez-cko

checkout_sdk/issuing/issuing_client.py

@@ -93,6 +93,8 @@ def update_card(self, card_id: str, update_card_request: UpdateCardRequest,
                 code encryption_key_required.
         Returns:
             ResponseWrapper with the update response, including encrypted_cvv when requested.
+            For a virtual card, the response may also include is_single_use, specifying whether
+            the card is set to expire after a single use. Physical cards never send it.
         """
         return self._api_client.patch(self.build_path(self.__ISSUING, self.__CARDS, card_id),
                                       self._sdk_authorization(),

tests/issuing/card_update_headers_wire_test.py

@@ -129,3 +129,15 @@ def test_a_successful_update_without_the_headers_has_no_encrypted_cvv(self, mock
 
         assert response.last_modified_date == '2026-06-01T10:00:00Z'
         assert not hasattr(response, 'encrypted_cvv')
+
+    def test_update_card_response_round_trips_is_single_use_for_virtual_cards(self, mock_sdk_configuration):
+        """The 2026-09-23 spec update split update-card-response into a virtual/physical
+        discriminator; the virtual variant adds is_single_use."""
+        client, _ = _build(mock_sdk_configuration, body='{'
+                           '"type":"virtual",'
+                           '"last_modified_date":"2026-06-01T10:00:00Z",'
+                           '"is_single_use":true}')
+
+        response = client.update_card('crd_123', UpdateCardRequest())
+
+        assert response.is_single_use is True