code: public ServiceFuture<Void> addUserAsync(String poolId, String nodeId, ComputeNodeUser user, final ServiceCallback<Void> serviceCallback) {
          return ServiceFuture.fromHeaderResponse(addUserWithServiceResponseAsync(poolId, nodeId, user), serviceCallback);
      }
docs: Adds a user account to the specified compute node.
  You can add a user account to a node only when it is in the idle or running state.
  
  @param poolId The ID of the pool that contains the compute node.
  @param nodeId The ID of the machine on which you want to create a user account.
  @param user The user account to be created.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object