DNS Proxy feature is now available in the Rapid release channel

## Feature [DNS Proxy feature](https://cloud.google.com/service-mesh/docs/operate-and-maintain/dns-proxy) is now available in the Rapid release channel. This feature requires sidecar version `1.21.5-asm.39` or later. ## Change This change affects clusters using both the `TRAFFIC_DIRECTOR` and `ISTIOD` control plane implementations. When using Cloud Service Mesh with Istio APIs, configuring an [unsupported field](https://cloud.google.com/service-mesh/docs/onboarding/unsupported-istio-apis) or value in an Istio Custom Resources will be reflected as an error in the Mesh status API. In some cases, the validation webhook will also reject unsupported API usage with an error message indicating the specific unsupported API. For more information, see [Common webhook error messages](https://cloud.google.com/service-mesh/docs/troubleshooting/troubleshoot-webhook#common%5Fwebhook%5Ferror%5Fmessages). You can mitigate these issues by amending the Istio Custom Resource to remove the specified unsupported API configuration. ## Feature Isolation support to prevent cross-region overflow is now available as a preview feature for `TRAFFIC_DIRECTOR` implementations of Cloud Service Mesh. For more information, see [Isolation for Cloud Service Mesh](https://cloud.google.com/service-mesh/docs/service-routing/isolation).