fedeway demo with remote sub-graphs

downstream service are copied from https://github.com/apollographql/federation-demo/tree/e24d9aca9d7a8fe9490ab53efeddc2ef8152f4a1

# shell A
$ git clone [email protected]:apollographql/federation-demo.git
$ cd federation-demo
$ git checkout e24d9aca9d7a8fe9490ab53efeddc2ef8152f4a1
$ npm ci
$ npm run start-services

# shell B
$ go run .
$ open http://localhost:8080/