@Override
    public String getContentType() {
        return Optional.ofNullable(clientResponse.getFirstHeader("Content-Type"))
                .map(NameValuePair::getValue)
                .orElseGet(super::getContentType);
    }
Proxies response back to client, keeps Content-Type header if it is present

@author olaa
@author freva
configserver/src/main/java/com/yahoo/vespa/config/server/http/ProxyResponse.java