auth-add-user-to-model.js

context: ({ req }) => {
	// get the user token from the headers
	const token = req.headers.authentication || '';
	
	// try to retrieve a user with the token
	const user = getUser(token);

	// optionally block the user
	// we could also check user roles/permissions here
	if (!user) throw new AuthenticationError('you must be logged in to query this schema');	

	// add the user to the context
	return { 
	  user, 
	  models: {
		User: generateUserModel({ user }),
		...
	  }
	};
},