
The code above creates a route group that is only accessible from a subdomain. The subdomain is determined by the {username} parameter. In this example, if the user visits amirreza.workspace.com, they will see a message indicating which subdomain the request came from.
This can be useful for creating different experiences for different users in the same domain. For example, you could use subdomains to give each user their own workspace where they can manage their own data.