code: public Map<String, Object> buildConsumerProperties() {
  		Map<String, Object> properties = buildCommonProperties();
  		properties.putAll(this.consumer.buildProperties());
  		return properties;
  	}
docs: Create an initial map of consumer properties from the state of this instance.
  <p>
  This allows you to add additional properties, if necessary, and override the
  default kafkaConsumerFactory bean.
  @return the consumer properties initialized with the customizations defined on this
  instance