@UnstableApi
    static RandomBackoffBuilder builderForRandom() {
        return new RandomBackoffBuilder();
    }
Returns a {@link RandomBackoffBuilder} that provides methods to configure
backoff delay which is a random value. The default values are as follows:
<ul>
  <li>{@code minDelayMillis}: {@value RandomBackoffBuilder#DEFAULT_MIN_DELAY_MILLIS}</li>
  <li>{@code maxDelayMillis}: {@value RandomBackoffBuilder#DEFAULT_MAX_DELAY_MILLIS}</li>
</ul>
core/src/main/java/com/linecorp/armeria/client/retry/Backoff.java