The URL template string that the route matches.

This string can contain fixed elements, i.e. `"/admin"`, capture elements, i.e. `"/{:controller}"`, capture elements optionally paired with regular expressions or named regular expression patterns, i.e. `"/{:id:\d+}"` or `"/{:id:ID}"`, the special wildcard capture, i.e. `"{:args}"`, or any combination thereof, i.e. `"/admin/{:controller}/{:id:\d+}/{:args}"`.