oc-mirror should always produce resources like release signatures

Proposed title of this feature request

oc-mirror should always produce resources like release signatures

What is the nature and description of the request?
When using https://docs.openshift.com/container-platform/4.12/installing/disconnected_install/installing-mirroring-disconnected.html#oc-mirror-updating-cluster-manifests_installing-mirroring-disconnected for disconnected environments, you will need the release signatures and also the updateservice config when working with osus.

Whe automated oc-mirror in a pipeline and make sure we always have the configuration even in case of disaster (keeping artifacts alway in gitlab ci/cd pipeline).

But if for some reason this goes wrong, there is no way with oc-mirror to get the release signatures or updateservice config.

We would like to see that oc-mirror get's an option to alway generate the release signatures and updateservice config.

Why does the customer need this? (List the business requirements here)
This would provide a more robust oc-mirror tool, makes sure we are better at adopting openshift in our environment.

List any affected packages or components.