above inputs into the actual types consumed by the connected XDS clients (typically Envoy). This is done by `Generators`, which register a function to build a given type. For example, there is a `RouteGenerator` responsible for building `Routes`. Along with the core Envoy XDS types, there are a few custom Istio types, such as our `NameTable` type used for DNS, as well as debug interfaces.

`Generators` get as input the `Proxy` (a representation of the current client), the current `PushContext`...