Deployment fails with Terraform Cloud

[JamesBelchamber]

When deploying a cluster following this guide using Terraform Cloud in Remote Execution Mode, the run fails with the following error:

timeout - last error: SSH authentication failed (core@<IP>:22): ssh: handshake failed: ssh: unable to authenticate, attempted methods [none], no supported methods remain

This is implied by the ssh-agent part of the guide, but since it's not explicitly called out (and the guide is otherwise quite fleshed out) I had a go and.. yup, not gonna work without that key 😅

I'm gonna have a go and see if there's any way to make this work - based on the results I can propose a PR for the guide.