fedora-image-uploader: configure message publishing
    
    The service will soon emit messages when new images are uploaded. This
    grants it access to publish under the fedora_image_uploader topic.
    
    Specific topics under the org.fedoraproject.prod prefix look like:
    
      fedora_image_uploader.azure.Fedora-Cloud-40.aarch64
      fedora_image_uploader.container.fedora.f40