This provisions the node and for the first time, will trigger a puppet run.

This puppet run will install the gateway's role including the routes back/forth
between production network and the staging network.

Note:

In the provision steps, prior to call puppet, we do need to install some setup
ourselves (route, ip_forward, etc...) to allow proxmox to continue the
provisioning of other nodes (coming). Puppet run installs the equivalent
instruction to make them persistent.

Related T1785
Related T1874

Depends on D1796

terraform init
terraform plan

This demos what it wants to do