Add tooling to spin up local environments

[simu]

Summary

Add shell script and make targets to spin up a kind-based local environment. The setup script prompts the user to setup a dev realm and admin user in an existing Keycloak instance. The PR doesn't provide tooling to spin up a local Keycloak instance at the moment.

Checklist

• PR contains a single logical change (to build a better changelog).
• Update the documentation.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking, dependency
  as they show up in the changelog.

[ccremer]

Just another source of inspiration: In K8up we also did a KIND setup, but based on make: https://github.com/k8up-io/k8up/tree/master/e2e

[tobru]

Vcluster uses k3s, here we're using kind: We should at least document that so that there is awareness that it isn't the same Kubernetes distro.

[simu]

Vcluster uses k3s, here we're using kind: We should at least document that so that there is awareness that it isn't the same Kubernetes distro.

I don't really care what we use, but APUB-155 (internal) explicitly asks for kind

[glrf]

Works pretty good, I was able to setup a test environment fairly quickly.

I only really care about the README change to reference the make command. The others are just nitpicks.

[bastjan]

It worked for me with make -C local-env setup after some trial and error.

The admin user has to have an email. Just toggling to email verified is not enough.

[bastjan]

LGTM. The instructions and guided steps now make it quite easy to setup the dev environment! 🧙‍♂️

[ccremer]

It worked well for me. Just small suggestions