Incrementally migrate from REST to GraphQL using the RestLink

You might still have some REST API endpoints that haven't been converted to GraphQL yet. In this lesson, we'll look at adding the RestLink. This allows us to add annotation to our GraphQL queries that tell Apollo to convert and re-direct to a REST endpoint behind the scenes. And since REST has no concept of types, we'll look at how to annotate types as well. This allows us to continue using a single way of querying for data in our components, without mixing fetch REST calls and GraphQL queries. It also provides a smooth upgrade path, since we can just remove the annotations once the conversion to GraphQL is finished on the backend.