components are installed into. Namespace definitions can be defined and specialized at the global, feature and component
level, with each lower level overriding the setting of the higher parent level. For example, if the global default
namespace is defined as:

```yaml
defaultNamespace: istio-system
```

and namespaces are specialized for the gateway feature and its components:

```yaml

// CertificateSigningRequestSpec contains the certificate request.
message CertificateSigningRequestSpec {
  // request contains an x509 certificate signing request encoded in a "CERTIFICATE REQUEST" PEM block.
  // When serialized as JSON or YAML, the data is additionally base64-encoded.
  // +listType=atomic
  optional bytes request = 1;

  // signerName indicates the requested signer, and is a qualified name.
  //

  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // Data is the serialized representation of the state.
  optional k8s.io.apimachinery.pkg.runtime.RawExtension data = 2;

  // Revision indicates the revision of the state represented by Data.
  optional int64 revision = 3;
}

     * Implementations should take appropriate action to handle the updated settings.
     *
     * Methods to this method may be made concurrently with [onStream]. But a calls to this method
     * are serialized.
     */
    open fun onSettings(
      connection: Http2Connection,
      settings: Settings,
    ) {}

    companion object {
      @JvmField
      val REFUSE_INCOMING_STREAMS: Listener =

  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // Data is the serialized representation of the state.
  optional k8s.io.apimachinery.pkg.runtime.RawExtension data = 2;

  // Revision indicates the revision of the state represented by Data.
  optional int64 revision = 3;
}

  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // data is the serialized representation of the state.
  optional k8s.io.apimachinery.pkg.runtime.RawExtension data = 2;

  // revision indicates the revision of the state represented by Data.
  optional int64 revision = 3;
}

        * Scale subresource now has a new <code>targetSelector</code> field in its status. This field supports the new set-based selectors supported
by Deployments, but in a serialized format.
     * Spec change:
        * Deployment’s [selector](http://kubernetes.io/docs/user-guide/labels/#label-selectors) is now more general (supports set-based selector; it only supported
equality-based selector in 1.1).