Create updated infrastructure diagram + documentation

[batpad]

Now that we've completed moving the infrastructure to Kubernetes and updated the way we run cronjobs and other services, we should update our infrastructure architecture diagram and add documentation where needed.

This is a bit separate from the developer documentation, which I think we mostly have in place - this is more of a high-level diagramatic representation of things.

@tovari would you have a link to the current / last updated infrastructure diagram that we have for reference?

@geohacker @sunu let's try and make sure we find some time to get this done next week or so.