Optional signing for pull/push and baseProfileName

[MaksimKlepikov]

My use case:

1. Collect seccomp profiles using SPO
2. Put these profiles as json files in Gitlab project
3. In Gitlab CI/CD pipeline push profiles as oci artifcats to Gitlab registry
4. Specify result oci profiles in SeccompProfile

The Gitlab itself is self-hosted in air-gapped environment.

The problem is in step 3, where spoc tries to sign it in non-interactive mode and also in air-gapped environment (even if https_proxy configured), so it fails with an error.

It would be nice to add documentation on how to use it in an air-gapped environment, or make signing optional.

[ccojocar]

I am not sure if skipping the signing is a good idea. I think you need to allow https://oauth2.sigstore.dev domain. Maybe making the OIDC provider configurable.