static RetryRule onStatusClass(Iterable<HttpStatusClass> statusClasses) {
        return onStatusClass(statusClasses, Backoff.ofDefault());
    }
Returns a newly created {@link RetryRule} that will retry with
the {@linkplain Backoff#ofDefault() default backoff} if the class of the response status is
one of the specified {@link HttpStatusClass}es.
core/src/main/java/com/linecorp/armeria/client/retry/RetryRule.java