protected <X extends AmazonWebServiceRequest> X appendUserAgent(
        X request, String userAgent) {
        request.getRequestClientOptions().appendUserAgent(userAgent);
        return request;
    }
Appends the given user agent to the given request.

@return the given request.
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/UploadObjectObserver.java