This lib implenments External-DNS webhook interface. External-DNS uses this interface to communicate with non-built-in DNS service provider.
The main trait is Provider, which defines the four functions of the webhook. Pass the implementor to Webhook::new, then Webhook::start to get the whole thing running.
Ref: https://github.com/kubernetes-sigs/external-dns/blob/master/docs/tutorials/webhook-provider.md