Implement Authentication for the communication between clients and GraphQL server

[bryankennedy]

The client computers in the exhibit system will need to connect to the GraphQL server over a local network and a public network depending on the exhibit setup. There will be aspects of the GraphQL data that we don't want to expose publicly. So we should require an auth token to query the GraphQL server.

One way to do this is to generate a JSON Web Token that's linked to various client machines. These tokens would be sent in the header of each GraphQL request.