Support auth.json for private composer repository

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

Regarding the latest feature request (#9093) it would probably be good to support composers `auth.json`[^1] file format for private repositories.

```
version: 2
registries:
private-packages:
type: composer-repository
url: https://
file: ${{secrets.COMPOSER_AUTH_JSON}}
```

The `COMPOSER_AUTH_JSON` secret would contain the JSON file content. This is also the common way to provide the file to any GitHub actions.

[^1]: https://getcomposer.org/doc/articles/authentication-for-private-packages.md#authentication-in-auth-json-per-project