docs: Instance marshall(ServiceInstance serviceInstance) {
  		String hostname = serviceInstance.getHost();
  		String managementPort = serviceInstance.getMetadata().get("management.port");
  		String port = managementPort == null ? String.valueOf(serviceInstance.getPort())
  				: managementPort;
  		String cluster = getClusterName(serviceInstance);
  		Boolean status = Boolean.TRUE; // TODO: where to get?
  		if (hostname != null && cluster != null && status != null) {
  			Instance instance = getInstance(hostname, port, cluster, status);
  
  			Map<String, String> metadata = serviceInstance.getMetadata();
  			boolean securePortEnabled = serviceInstance.isSecure();
  
  			addMetadata(instance, hostname, port, securePortEnabled, port, metadata);
  
  			return instance;
  		}
  		else {
  			return null;
  		}
  	}