Add Challenge CRD as a Kubernetes API extension

[gree-gorey]

Background on k8s CRD: https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/

We can add challenge object with it's yaml config looking smth like:

apiVersion: "kctf.dev/v1"
kind: Challenge
metadata:
  name: mychal
spec:
  public: true
  healthcheck: false
  https: true
  dns: true
  autoscaling: {}
  # any other arbitrary fields

On the k8s cluster size there will be a controller (needs to be implemented): it will just watch for creation/update of challenge resource in the cluster, and set it up upon creation/update. E.g. if you change public: true to public: false it will delete service for that challenge.

Some advantages of having this:

1. challenge will become a 1st-class k8s API citizen, allowing to use kubectl list challenges or kubectl describe challenge mychal
2. it allows us to use standard config (k8s yaml) and standard commands like kubectl create challenge mychal or kubectl delete challenge mychal
3. we can take away some steps from being executed locally to k8s controller, e.g. building an image for challenge: the controller would create a Job for building an image and then creates a Deployment for challenge
4. this can also help with versioning: we can specify it with apiVersion: "kctf.dev/v1", this is again a standard way of k8s API versioning

[gree-gorey]

I am going to put together some minimal proof of concept to see if that would work and how difficult/convenient that would be.

[aliciafmachado]

I guess it's done :)