RepeatDataPathResource/RepeatDataPathTrailingResource showcase test fails

At least part of the problem is the null assert operators used in the URL construction:

```dart
Future repeatDataPathResource(RepeatRequest request) async {
final url = Uri.https(
_host,
'/v1beta1/repeat/${request.info!.fString}/${request.info!.fChild!.fString}/bool/${request.info!.fBool}:pathresource',
```

I actually don't know what should happen if any of the URL components are not set.