Package conversion provides interface definitions that an API Type needs to implement for it to be supported by the generic conversion webhook handler defined under pkg/webhook/conversion.
Convertible defines capability of a type to convertible i.e. it can be converted to/from a hub type.
Hub marks that a given type is the hub type for conversion. This means that all conversions will first convert to the hub type, then convert from the hub type to the destination type. All types besides the hub type should implement Convertible.