Changes to GET /:stack/adminconfig/v2/maintenance-windows/preferences

added the optional property preferredSchedule to the response with the 200 status

added the optional property warning to the response with the 200 status

added the required property changeFreezes/customerInitiatedFreezes/items/ticketsV2 to the response with the 200 status

added the required property changeFreezes/splunkInitiatedFreezes/items/ticketsV2 to the response with the 200 status

endpoint added