How to assign a consumer group to a partition / topic

Assign a consumer to a list of partitions is not incremental.

// Set the consumer group
var config = new ConsumerConfig
{
  GroupId = "test-app",
  BootstrapServers = "localhost:9092",
  Debug = "generic, broker, topic, metadata, consumer"
};
var builder = new ConsumerBuilder<string, string>(config);