default RetryRule orElse(RetryRule other) {
        return RetryRuleUtil.orElse(this, requireNonNull(other, "other"));
    }
Returns a composed {@link RetryRule} that represents a logical OR of this {@link RetryRule} and another.
If this {@link RetryRule} completes with {@link RetryDecision#next()}, then other {@link RetryRule}
is evaluated.
core/src/main/java/com/linecorp/armeria/client/retry/RetryRule.java