feat: SD-Core CUPS howto

[markbeierl]

Description

Adds a how to section for deploying CUPS SD-Core.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [ ] I have added tests that validate the behaviour of the software
• [ ] I validated that new and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have bumped the version of the library

[markbeierl]

I'm using this as an example howto that I find complete enough to use: https://discourse.ubuntu.com/t/multi-node/35727

What really bothers me in documentation is when I am left trying to get the information that is needed. For example, bootstrapping a juju controller. We start here https://juju.is/docs/juju/, nothing obvious in any of the left for how to bootstrap. Found it here https://juju.is/docs/juju/manage-controllers#heading--create-a-controller, which really says nothing about bootstrapping a kubernetes cluster using a kubeconfig.yaml file. So, in absence of upstream documentation, how can we make the user successful here?

[gruyaume]

I'm using this as an example howto that I find complete enough to use: https://discourse.ubuntu.com/t/multi-node/35727

@markbeierl What you linked here is a tutorial, not a how-to guide.

The tutorial should walk the user from beginning to end with the assumption that this is the first time the user is interacting with our stuff. The how-to guide assumes the user already has been deploying SD-Core CUPS but needs a refresher.

What we are building in this PR is a how-to guide.

For reference: https://diataxis.fr/tutorials-how-to/