@Override
    public HttpResponse toHttpResponse(ResponseHeaders responseHeaders) {
        final ResponseHeaders responseHeadersWithBoundary = injectBoundary(boundary, responseHeaders);
        return HttpResponse.of(responseHeadersWithBoundary, this);
    }
Returns a random boundary used for encoding multipart messages.
core/src/main/java/com/linecorp/armeria/common/multipart/DefaultMultipart.java