Question - When to call UseMqtt() for Kestrel

Looking at the ASPNET Core example for Kestrel it has the following code during configuration...
```
opts.ListenAnyIP(1883, l => l.UseMqtt());
opts.ListenAnyIP(5000); // Default HTTP pipeline
```

When do I choose to invoke `UseMqtt()` and when do I not?

I *think* it is whether or not I'm switching to a TCP connection versus forwarding an HTTP connection, but I want to make sure before I do something stupid and blow up my app.

Start with the ASP.NET Core Kestrel example containing the ListenAnyIP calls for ports 1883 and 5000, then inspect how UseMqtt() is described and used there. Done means documenting when UseMqtt() should be invoked and how that relates to the two listener configurations.

Written by the indexing model from the issue text.