Currently, only the image parameter is supported, which results in Syft invoked with docker:<image-value>. We will almost assuredly need a way to connect to / scan external registries (Syft supports this).

One option to investigate: can we use docker/login-action to specify registry and/or credentials that later get used by the scan-action? this would probably end up providing a better experience for the end user than having to configure credentials multiple times.

Also see: anchore/syft#502