Small improvement to API client access

In the MVC project, you're actually spinning up a real HttpClient to make requests. I would assume that even if you were scaling this, you'd ship the browser client with the back end. If not, your solution would be preferred, but in this example it might be worth noting you can use an in-memory representation of the same API and get all the same benefits without causing any real HTTP traffic. The result (should be) better performing.