Add client example

[johanbrandhorst]

@yurishkuro showed that users of this repository could benefit of a good example of a client using the server. I would like the following to be shown with this client:

1. It should connect to the server over TLS (using the self signed cert)
2. It should attempt to create a user that is not an admin, and parse the error returned.
3. It should then create a user that is an admin.
4. Finally it should list all users, showing how to iterate over a server side stream.