armeria response logger with LTSV format

ResponseLTSVLoggingService.java

public static class ResponseLTSVLoggingService<I extends Request, O extends Response>
        extends DecoratingService<I, O, I, O> {

    public ResponseLTSVLoggingService(Service<? super I, ? extends O> delegate) {
        super(delegate);
    }

    @Override
    public O serve(ServiceRequestContext ctx, I req) throws Exception {
        ctx.log().addListener(this::logResponse, RequestLogAvailability.COMPLETE);
        return delegate().serve(ctx, req);
    }

    protected void logResponse(RequestLog log) {
        final Logger logger = ((ServiceRequestContext) log.context()).logger();
        logger.info(responseLogLTSV((DefaultRequestLog) log));
    }

    private String responseLogLTSV(DefaultRequestLog log) {
        final HttpHeaders headers = (HttpHeaders) log.requestEnvelope();
        final String userAgent = headers.get(HttpHeaderNames.USER_AGENT);
        final String scheme = headers.get(HttpHeaderNames.SCHEME);
        final String authority = headers.get(HttpHeaderNames.AUTHORITY);

        final StringBuilder sb = new StringBuilder();
        // request
        sb.append("time:");
        TextFormatter.appendEpoch(sb, log.requestStartTimeMillis());
        sb.append("\t");
        sb.append("method:").append(log.method()).append("\t");
        sb.append("scheme:").append(scheme).append("\t");
        sb.append("host:").append(log.host()).append("\t");
        sb.append("authority:").append(authority).append("\t");
        sb.append("path:").append(log.path()).append("\t");
        sb.append("request_length:").append(log.requestLength()).append("\t");
        sb.append("user_agent:").append(userAgent).append("\t");
        // response
        sb.append("status:").append(log.statusCode()).append("\t");
        sb.append("duration_millis:").append(log.totalDurationNanos() / 1000_000).append("\t");
        sb.append("response_length:").append(log.responseLength()).append("\t");
        sb.append("response_cause:").append(log.responseCause());
        return sb.toString();
    }
}