public ClientCacheControlBuilder staleIfError(@Nullable Duration staleIfError) {
        staleIfErrorSeconds = validateDuration(staleIfError, "staleIfError");
        return this;
    }
Enables or disables the {@code "stale-if-error"} directive.

@param staleIfError the value of the directive to enable, or {@code null} to disable.
core/src/main/java/com/linecorp/armeria/common/ClientCacheControlBuilder.java