Simple example of stitching together schema from two different GraphQL servers

This example will stitch together the Author and Book GraphQL services and extend the Author type to add the ability to get information about book by the author.

Additionally, we will do some basic transformation to the Book service to remove and rename root level queries.

To start up the servers, run

npm install
npm start

Then in your browser:
     the URL "http://localhost:3000/" will show you a GraphQL client for the gateway.
     the URL "http://localhost:3001/" will show you a GraphQL client for the Author service.
     the URL "http://localhost:3002/" will show you a GraphQL client for the Book service.

The gateway allows you to get information about authors and book in a single query, even though the Author and Book services do now offer information about each other.

Example gateway request:

{
  authors {
    name
    books {
      title
      review
    }
  }
}

Example gateway response:

{
  "data": {
    "authors": [
      {
        "name": "J.K. Rowling",
        "books": [
          {
            "title": "Harry Potter and the Chamber of Secrets",
            "review": 4.4
          },
          {
            "title": "Fantastic Beasts and Where to Find Them",
            "review": 4
          },
          {
            "title": "The Casual Vacancy",
            "review": 3.3
          }
        ]
      },
      ...