[DOCS]: Fully document the infrastructure.

[cielf]

Context for documentation change

We know there are things that are in the heads of only one or two people. That needs to change.

Proposed solution

A full description of the infrastructure -- everything we need to know.

Question: Where do we put this?

What do we do about information that really should be in a primary and backup's control?

Collaborators

This is mainly @dorner and @awwaiid ! We might need to reach out to @edwinthinks and @seanmarcia.

[cielf]

Noting that we musn't forget fly.io (which has our metabase instance on it).