Implement block_traffic::block_routes middleware

[Turbo87]

This corresponds roughly to

crates.io/src/router.rs

Lines 190 to 195 in bbcc099

	// Allow blocking individual routes by their pattern through the `BLOCKED_ROUTES`
	// environment variable. This is not in a middleware because we need access to
	// `RoutePattern` before executing the response handler.
	if req.app().config.blocked_routes.contains(pattern) {
	return Ok(RouteBlocked.response().unwrap());
	}

Note that with axum we can implement this as a middleware because axum middlewares run after the routing layer by default.