Expose ID field on globals to GraphQL

[evelynhathaway]

When querying a global multiple times with Apollo GraphQL, an error is returned about how it doesn't know the cache key.

Apollo GraphQL's default behavior for InMemoryCache is to cached based off of id. Globals in Payload have an id as well as globalType available to the REST API once saved for the first time. If Payload were to expose these fields to GraphQL, fixing the caching error would be as simple as querying the id field.

Currently, the workaround is to manually specify __typename as a keyField for the cache, or to write a custom merge function.

new InMemoryCache({
  typePolicies: {
    MyGlobal: {
      keyFields: ["__typename"],
    },
  },
});