Add Support for OpenTofu Provider Signing Key

[douglasflagg]

BUSINESS PROBLEM

Currently there is no signing key configured for the Venafi provider on the OpenTofu registry so users see a warning like this when downloading the provider through the OpenTofu registry (when running 'tofu init').

[WARN]  Skipping GPG validation of provider package /var/folders/... as no keys were provided by the registry. See https://github.com/opentofu/opentofu/pull/309 for more information.
- Installed venafi/venafi v0.21.1. Signature validation was skipped due to the registry not containing GPG keys for this provider
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PROPOSED SOLUTION

Please add the Provider Signing Key for the Venafi provider to the OpenTofu Registry. Here are the steps.

CURRENT ALTERNATIVES

Not certain there are others save for not supporting signing keys for OpenTofu.

VENAFI EXPERIENCE

I have been using Venafi since 2022 and use it at almost every week.