Route<T>.join constructor
Implementation
factory Route.join(Route<T> a, Route<T> b) {
var start = a.path.replaceAll(_straySlashes, '');
var end = b.path.replaceAll(_straySlashes, '');
return Route('$start/$end'.replaceAll(_straySlashes, ''),
method: b.method, handlers: b.handlers);
}