[GOT-63] Document the Terraform setup

[jsign]

This GH issue is getting ahead of a PR that might be merged soon.

We should think if it's worth adding documentation to let external validators leverage the Terraform setup.

Leaving it on-hold until that PR is merged.

_GOT-63

[brunocalza]

There's still some thinking to do about who is the final user of this tooling and which things should be included in this setup and which things should not. As we saw yesterday by spinning up a new validator, the Terraform setup wasn't perfect. There was some configuration that we needed to do after the terraform config was applied.

Maybe we can have multiple Terraform setups considering multiple scenarios or personas (with/without healthbot, with/without grafana database, with/without cron, with/without analytics, ...)

I'm not planning to merge that PR (leaving it as a draft) as it is now because it can be confusing.