Configuring the default broker class

apiVersion: operator.knative.dev/v1beta1
kind: KnativeEventing
metadata:
  name: knative-eventing
  namespace: knative-eventing
spec:
  defaultBrokerClass: Kafka (1)
  config: (2)
    config-br-defaults: (3)
      default-br-config: |
        clusterDefault: (4)
          brokerClass: Kafka
          apiVersion: v1
          kind: configmap
          name: kafka-broker-config (5)
          namespace: knative-eventing (6)
        namespaceDefaults: (7)
          my-namespace:
            brokerClass: MTChannelBasedBroker
            apiVersion: v1
            kind: configmap
            name: config-br-default-channel (8)
            namespace: knative-eventing (9)
...