Allow dots in URL Mapping's prefix section

[Jiron]

You can't add dots in the prefix path. When trying to map socket.io for example, this will cause some trouble. You will have to change the path on where socket.io runs on your server to a path which does not include a dot, for example /socketio. I did it like so:

const io = new Server(server, {
    path: '/socketio'
});

What's weird is that dots are allowed in the "target" section, so I could route it to lets say somerandomurl.com/socket.io, but you can't add dots in the "prefix" section.
When adding a dot in the "prefix" section, you'll just be hit with an error:

In my opinion, it would be great to just allow it as I do not see what could cause issues with it. Socket.io uses /socket.io as the default path so it's just one extra step you have to think about when working with activities.

Next to that the error isn't really descriptive. Took me a second to understand that the dot was the issue.

[matthova]

While the workaround is simple (just remap it to socketio) I appreciate that this will be a common painpoint. Plus /socket.io is a valid url path. Thanks for flagging. We'll see if there's a path forward