Prevent IngressClass from being deleted/recreated

[dcarley]

What this PR does / why we need it:

This conditional is intended to not create the IngressClass if it has
already been created outside of the chart, e.g. manually prior to it
being included in v2.3.0

The previous implementation that used lookup to check if the
IngressClass existed caused the template to be omitted from the chart
and Helm would delete it on the second release, then it would be
recreated on the third release and so on.

Fix this by checking whether the existing IngressClass was installed
by this chart based on Helm's annotations. The conditionals have been
refactored to set a variable (like the CRDs template) since the
conditions are now more complex and Helm makes it hard to safely lookup
nested values.

Which issue this PR fixes

• fixes IngressClass being deleted and recreated #512

Special notes for your reviewer:

I can't see any automated regression tests that cover subtle problems
like this and I'm not sure you'd want to script them, so here's the
manual testing that I've performed.

Doesn't create when there is an existing IngressClass:

$ kubectl apply -f- <<EOS
apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  name: kong
spec:
  controller: konghq.com/ingress-controller
EOS

ingressclass.networking.k8s.io/kong created
$ helm upgrade kong charts/kong/ --install --set ingressController.installCRDs=false >/dev/null
$ helm get manifest kong | grep IngressClass
$ helm upgrade kong charts/kong/ --install --set ingressController.installCRDs=false >/dev/null
$ helm get manifest kong | grep IngressClass

Does create and doesn't delete when there is no existing IngressClass:

$ kubectl delete IngressClass/kong
ingressclass.networking.k8s.io "kong" deleted
$ helm upgrade kong charts/kong/ --install --set ingressController.installCRDs=false >/dev/null
$ helm get manifest kong | grep IngressClass
kind: IngressClass
$ helm upgrade kong charts/kong/ --install --set ingressController.installCRDs=false >/dev/null
$ helm get manifest kong | grep IngressClass
kind: IngressClass

Checklist

• PR is based off the current tip of the next branch and targets next, not main
• Commits follow the Kong commit message guidelines

[CLAassistant]

All committers have signed the CLA.

[rainest]

Upgrade testing has been something we've wanted to add for a while now; absent that we do manual verification at the time of the PR like you've done here.

@dcarley LGTM, we can go ahead and merge once you've signed the CLA.

[dcarley]

Just waiting for the CLA to be signed on behalf of my employer @circleci first. Shouldn't be too long.

[rainest]

@dcarley just checking in on this, had you heard back from your employer yet?

[z00b]

hi @rainest i'd be happy to sign on behalf of CircleCI, but i don't seem to be able to do this on this PR? cla assistant shows that i have authorized the CLA but either that's pointing to just me personally or @dcarley 's PR isn't associated with CircleCI. any thoughts on how to proceed?

[dcarley]

I signed it after you, based on the process for organisations that was discussed in Kong/kong#5070, so it looks like we're good to go now. I'll let the rest of our team know that they can/should sign the CLA individually in future 🚀