Specify additional labels and annotations for the secret created by the User Operator.

.An example showing the `KafkaUserTemplate`
[source,yaml,subs=attributes+]
----
apiVersion: {KafkaUserApiVersion}
kind: KafkaUser
metadata:
  name: my-user
  labels:
    strimzi.io/cluster: my-cluster
spec:
  authentication:
    type: tls
  template:
    secret:
      metadata:
        labels:
          label1: value1
        annotations:
          anno1: value1
  # ...
----
