private static URI concatenated(URI base, String... parts) {
        return base.resolve(Stream.of(parts).map(part -> URLEncoder.encode(part, UTF_8)).collect(joining("/")) + "/");
    }
Returns an authenticated request from the given input. Override this for, e.g., request signing.
hosted-api/src/main/java/ai/vespa/hosted/api/ControllerHttpClient.java