@CheckReturnValue
    default SplitHttpRequest split() {
        return split(defaultSubscriberExecutor());
    }
Returns a new {@link SplitHttpRequest} which splits a stream of {@link HttpObject}s into
{@link HttpData}s and an HTTP trailers.
{@link SplitHttpRequest#trailers()} might not complete until the entire request body is consumed
completely.
core/src/main/java/com/linecorp/armeria/common/HttpRequest.java