I would like to cache a Network Image from an S3 bucket URL against an id or key. I tried to use the key: parameter but it didn't work. Please advise how I can achieve this. Heres the Cached Network Image code with the 'key' parameter that doesn't seem to do what I intend.

```
       CachedNetworkImage(
           key: Key(uni['university_name'].toString()), // Doesn't seem to do the job
            imageUrl: uni['image_url'],
            placeholder: (context, url) => CardPlaceHolder(),
            errorWidget: (context, url, error) => Padding(
              padding: EdgeInsets.all(21),
              child: Icon(
                Icons.error,
                size: 30,
                color: Colors.red.withOpacity(0.8),
              ),
            ),
            imageBuilder: (context, imageProvider) => ...

```