Document that/why we don't use Helm's CRD installation mechanism

[irbekrm]

Cert-manager's Helm chart does not use Helm's CRD installation mechanism because it does not allow for CRD update, see https://github.com/helm/community/blob/f9e06c16d89ccea1bea77c01a6a96ae3b309f823/architecture/crds.md

This can cause confusion for folks, see i.e https://kubernetes.slack.com/archives/C4NV3DWUC/p1676635914363249?thread_ts=1676588335.690979&cid=C4NV3DWUC cert-manager/cert-manager#5794

We should document

• what is the difference (i.e helm show crds doesn't work)
• why we are doing this

[hawksight]

I think I might have covered this, or at least a good attempt to:

• https://cert-manager.io/docs/installation/helm/#3-install-customresourcedefinitions
• https://cert-manager.io/docs/installation/helm/#crd-considerations

@irbekrm - appreciate your input if I have covered all the main differences

See: #1248

[hawksight]

/assign

[maelvls]

Are you still working on this? @hawksight

(it's totally OK if you aren't 😅)

[hawksight]

I actually did document this previously, here: https://cert-manager.io/v1.14-docs/installation/helm/#crd-considerations
I think this was removed in v1.15 release due to the change in CRD annotations that were added to the chart?

I guess from a user perspective, do we still behave differently to standard helm and do we document this difference?