I'm doing this:

```
$link = $node->field_link->first();
if ($link) {
  $url = $link->getUrl()->toString();
  ...
}

```

If the value in the link field is `/node/123` but there is a URL alias defined as:

```
Alias: /about-us    System path: /node/123

```

I get `/about-us` in `$url`. I want to get `/node/123`.

How do I get the raw url value instead of the aliased value?