public Optional<ServiceReferencePatch> service() {
        return Optional.ofNullable(this.service);
    }
@return service is a reference to the service for this webhook. Either service or url must be specified.

If the webhook is running within the cluster, then you should use `service`.
sdk/java/src/main/java/com/pulumi/kubernetes/apiextensions/v1/outputs/WebhookClientConfigPatch.java