private static SubmitResult toSubmitResult(HttpResponse<byte[]> response) {
        Inspector rootObject = toInspector(response);
        return new SubmitResult(rootObject.field("message").asString(),
                                rootObject.field("build").asLong());
    }
Returns the "message" element contained in the JSON formatted response.
hosted-api/src/main/java/ai/vespa/hosted/api/ControllerHttpClient.java