static <T extends Response> RetryRuleWithContent<T> onStatusClass(HttpStatusClass statusClass,
                                                                      Backoff backoff) {
        return RetryRuleWithContent.<T>builder().onStatusClass(statusClass).thenBackoff(backoff);
    }
Returns a newly created {@link RetryRuleWithContent} that will retry with the specified {@link Backoff}
if the class of the response status is the specified {@link HttpStatusClass}.
core/src/main/java/com/linecorp/armeria/client/retry/RetryRuleWithContent.java