You can change URLs in the response body returned from backend services and return a different URL to the client. This page contains an example of changing URLs in the response body using the replaceAll method.
responseBodyTextToClient=responseBodyTextToClient.replaceAll('https://geomap.reteunitaria.piemonte.it/ws/gsareprot/rp-01/areeprotwfs/wfs_gsareprot_1?', 'https://api.apinizer.com/apigateway/geoservis');
responseBodyTextToClient=responseBodyTextToClient.replaceAll('http://geomap.reteunitaria.piemonte.it/ws/gsareprot/rp-01/areeprotwfs/wfs_gsareprot_1?', 'https://api.apinizer.com/apigateway/geoservis');