Kubernetes namespace post and pre delete hooks
You can have a webhook to perform any task/operation that you want to do. When a a request to delete a namespace comes to kubernetes API server the webhook will be called by kubernetes API server automatically. A webhook is an http/https endpoint to a running piece of software which could be running in the Kubernetes cluster itself or somewhere else. A webhook need to be registered to Kubernetes API server to be able receive the request from the API server.