private static Optional<String> findClientVersion(HttpRequest request) {
        String versionHeader = request.getHeader(Headers.CLIENT_VERSION);
        if (versionHeader != null) {
            return Optional.of(versionHeader);
        }
        return Optional.ofNullable(request.getHeader("User-Agent"))
                .map(USER_AGENT_PATTERN::matcher)
                .filter(Matcher::matches)
                .map(matcher -> matcher.group(1));
    }
Accept feeds from outside the Vespa cluster.

@author Steinar Knutsen
vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/FeedHandler.java