private static boolean isHttpStatusCode(int code) {
        switch (code) {
            case Response.Status.OK :
            case Response.Status.MOVED_PERMANENTLY :
            case Response.Status.FOUND :
            case Response.Status.TEMPORARY_REDIRECT :
            case Response.Status.BAD_REQUEST :
            case Response.Status.UNAUTHORIZED  :
            case Response.Status.FORBIDDEN :
            case Response.Status.NOT_FOUND :
            case Response.Status.METHOD_NOT_ALLOWED :
            case Response.Status.NOT_ACCEPTABLE :
            case Response.Status.REQUEST_TIMEOUT :
            case Response.Status.INTERNAL_SERVER_ERROR :
            case Response.Status.NOT_IMPLEMENTED :
            case Response.Status.SERVICE_UNAVAILABLE :
            case Response.Status.VERSION_NOT_SUPPORTED :
            case GATEWAY_TIMEOUT :
            case BAD_GATEWAY :
            case PRECONDITION_REQUIRED :
            case TOO_MANY_REQUESTS :
            case REQUEST_HEADER_FIELDS_TOO_LARGE :
            case NETWORK_AUTHENTICATION_REQUIRED :
                return true;
            default:
                return false;
        }
    }
(during normal execution) return 200 unless this is not a success or a 4xx error is requested.

@param isSuccess whether or not the response represents a success
@param mainError the main error of the response, if any
@param allErrors all the errors of the response, if any
@return the status code of the given response
container-core/src/main/java/com/yahoo/container/jdisc/VespaHeaders.java