document allow_ad_hoc_containers setting.

part of kiali/kiali#5028

content/en/docs/FAQ/installation.md

@@ -66,6 +66,7 @@ OPERATOR_NAMESPACE="$(kubectl get deployments --all-namespaces  | grep kiali-ope
 
 - `ALLOW_AD_HOC_KIALI_NAMESPACE`: must be `true` or `false`. If `true`, the operator will be allowed to install the Kiali Server in any namespace, regardless of which namespace the Kiali CR is created. If `false`, the operator will only install the Kiali Server in the same namespace where the Kiali CR is created - any attempt to do otherwise will cause the operator to abort the Kiali Server installation.
 - `ALLOW_AD_HOC_KIALI_IMAGE`: must be `true` or `false`. If `true`, the operator will be allowed to install the Kiali Server with a custom container image as defined in the Kiali CR's `spec.deployment.image_name` and/or `spec.deployment.image_version`. If `false`, the operator will only install the Kiali Server with the default image. If a Kiali CR is created with `spec.deployment.image_name` or `spec.deployment.image_version` defined, the operator will abort the Kiali Server installation.
+- `ALLOW_AD_HOC_CONTAINERS`: must be `true` or `false`. If `true`, the operator will be allowed to install additional containers in the Kiali Server pod as defined by the Kiali CR's `spec.deployment.additional_pod_containers_yaml`. If `false`, the operator will not install any additional containers - any attempt to set that Kiali CR setting will cause the operator to abort the Kiali Server installation.
 - `ALLOW_SECURITY_CONTEXT_OVERRIDE`: must be `true` or `false`. If `true`, the operator will be allowed to install the Kiali Server container with a fully customizable securityContext as defined by the user in the Kial CR. If `false`, the operator will only allow the user to add settings to the securityContext; any attempt to override the default settings in the securityContext will be ignored.
 - `ANSIBLE_DEBUG_LOGS`: must be `true` or `false`. When `true`, turns on debug logging within the Operator SDK. For details, see the [docs here](https://sdk.operatorframework.io/docs/building-operators/ansible/development-tips/#viewing-the-ansible-logs).
 - `ANSIBLE_VERBOSITY_KIALI_KIALI_IO`: Controls how verbose the operator logs are - the higher the value the more output is logged. For details, see the [docs here](https://sdk.operatorframework.io/docs/building-operators/ansible/reference/advanced_options/#ansible-verbosity).