Hi, I'm trying to get LocalStack set up for integration testing and having a lot of trouble building CloudFormation templates that include nested stacks referenced via the `TemplateURL` property. Is this just not a thing that works in LocalStack? I've tried setting TemplateURL to a local file as well as to an object in an S3 bucket created with LocalStack.

For example if I call `create-stack` on a `template.yaml` containing the following:
```
Resources:
  SNSTopics:
    Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: http://localhost:4572/artifacts/sns.yaml
```

...the stack builds but the referenced `sns.yaml` stack does not get built; whereas if I call `create-stack` directly on the referenced file it builds fine.

Thanks for any help/advice you can give!
if hasattr(entity, 'physical_resource_id'):
        return entity.physical_resource_id
    
    types_with_ref_as_id_or_name = (apigw_models.RestAPI, apigw_models.Resource)
    attr_candidates = ['function_arn', 'Arn', 'Ref', 'id', 'Id', 'name', 'Name']
    for attr in attr_candidates:
        if hasattr(entity, attr):
            if attr in ['id', 'name'] and not isinstance(entity, types_with_ref_as_id_or_name):
                LOG.warning('Unable to find ARN, using "%s" instead: %s - %s',
                            attr, resource_json, entity)
            return getattr(entity, attr)
        if hasattr(entity, 'get_cfn_attribute'):
            try:
                result = entity.get_cfn_attribute(attr)
                if result:
                    return result
            except Exception:
                pass
    
    if hasattr(entity, 'params'):
        for key, value in (entity.params or {}).items():
            if key.endswith('Name'):
                return value
def convert_objs_to_ids(resource_json):