Proxmox OpenTofu configuration

1. Add the following .tfvars:
   1. proxmox_user - Proxmox username with realm (e.g. user@pve)
   2. proxmox_server_ip - Proxmox server IP address
   3. proxmox_api_key_name - Proxmox API key name
   4. proxmox_api_key_secret - Proxmox API key secret
2. Run tofu plan
3. Run tofu apply

Shoutout to https://culturelinux.github.io/doc/iac/opentofu/ for the jumpstart.