type Callbacks interface {
	// OnFetchRequest is called for each Fetch request. Returning an error will end processing of the
	// request and respond with an error.
	OnFetchRequest(context.Context, *discovery.DiscoveryRequest) error
	// OnFetchResponse is called immediately prior to sending a response.
	OnFetchResponse(*discovery.DiscoveryRequest, *discovery.DiscoveryResponse)
}

type Server interface {
	Fetch(context.Context, *discovery.DiscoveryRequest) (*discovery.DiscoveryResponse, error)
}