DisableTrustOnFirstUse option for OIDC provisioner

[siiimooon]

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Issue details

I would like the option DisableTrustOnFirstUse for the OIDC provisioner too, just like the cloud provisioners (Azure, AWS, GCP). Ref. https://github.com/smallstep/certificates/blob/master/authority/provisioner/azure.go#L117

Why is this needed?

I have integrated Smallstep CA with my Kubernetes environment, which has a OIDC-backed service account issuer. This enables my Kubernetes workloads to fetch certificates based on their service account token. The OIDC provisioner is brilliant for this purpose, as it fetches the signing key dynamically from the cluster OIDC endpoint (rather than hardcoding the service account signing key using the K8SSA provisioner). Sometimes the Kubernetes-based workloads crash and restart, but the service account token is not rotated on a container restart - forcing me to reschedule the error-prone pods to make it obtain a new and unused token. Allowing reuse of a token would simplify operations. Token reuse should still be disallowed by default (as-is), but possible to allow in scenarios where one can accept the risk.

If the change sounds reasonable, I would be happy to file PRs with the change. AFAIK, this would require changes in three repositories (smallstep/certificates, smallstep/linkedca, and smallstep/doc).