type ShardKey struct {
	Cluster  cluster.ID
	Provider provider.ID
}

func (sk ShardKey) String() string {
	return string(sk.Provider) + "/" + string(sk.Cluster) // format: %s/%s
}

// MarshalText implements the TextMarshaler interface (for json key usage)
func (sk ShardKey) MarshalText() (text []byte, err error) {
	return []byte(sk.String()), nil
}