@SafeVarargs
    static <T> StreamMessage<T> concat(Publisher<? extends T>... publishers) {
        requireNonNull(publishers, "publishers");
        return concat(ImmutableList.copyOf(publishers));
    }
Returns a concatenated {@link StreamMessage} which relays items of the specified array of
{@link Publisher}s in order, non-overlappingly, one after the other finishes.
core/src/main/java/com/linecorp/armeria/common/stream/StreamMessage.java