Router has now been edited to take three parameters

I was linked to this tutorial from [this YouTube video](https://www.youtube.com/watch?v=Sr5QcYyGrCo). It was great to follow along!

One thing that went wrong, however, are the Routing commands. It seems that newer versions of the `router` crate require `router.get`, `router.post` etc. to be used with [three parameters](https://docs.rs/router/0.5.1/router/), the third one being a symbolic name to refer to the route to later (such as in when using `router::url_for`).