Define and upload a Sentinel policy set to HCP Terraform with soft-mandatory enforcement

Steps

1. Create a Sentinel policy file (e.g., `enforce-tags.sentinel`) that imports `tfplan/v2` and checks `tfplan.resource_changes` for required tag keys.
2. Create a `sentinel.hcl` manifest file listing each policy file and its enforcement level (`soft-mandatory`, `hard-mandatory`, or `advisory`).
3. In HCP Terraform navigate to Settings > Policy Sets > Connect a new policy set and point it at the VCS repository containing your Sentinel files, or upload a tarball via the API using `PUT /api/v2/policies/{policy-id}/upload`.
4. Attach the policy set to one or more workspaces or to the entire organization from the policy set configuration page.
5. Trigger a plan run in an attached workspace; after the plan phase the policy check phase runs automatically and posts pass/fail results on the run page.
6. For `soft-mandatory` failures a workspace admin can override the failure; `hard-mandatory` failures block the run entirely and cannot be overridden.