default Set<TransientServiceOption> transientServiceOptions() {
        return Flags.transientServiceOptions();
    }
Returns the {@link Set} of {@link TransientServiceOption}s that are enabled for this
{@link TransientService}. This returns {@link Flags#transientServiceOptions()} if you didn't
specify any {@link TransientServiceOption}s using
{@link TransientServiceBuilder#transientServiceOptions(TransientServiceOption...)} when you create
this {@link TransientService}.
core/src/main/java/com/linecorp/armeria/server/TransientService.java