This commit let's users override the apiVersion referenced in this
chart so that the chart can be used with newer cert-manager releases.
(script/cert-manager/install-cert-manager.sh installs 0.13.0 when
current version is 1.2.0...)
Fixes#68
### Motivation
cert-manager apiVersion changed after cert-manager 1.0.0 was released, which prevents the chart from provisionning certificates with newer cert-manager installation because of an incompatible apiVersion.
I have a cluster with cert-manager >1.0.0 installed, making `apiVersion` overridable makes it easy for me to install pulsar on that cluster
### Modifications
I introduced the value `certs.internal_issuer.apiVersion`, which by default uses the apiVersion that was previously hardcoded (`cert-manager.io/v1alpha2`)
I replaced all occurrences of that apiVersion by a reference to the value so that users can override it to `cert-manager.io/v1` if they have a newer version of cert-manager installed.
### Verifying this change
- [x] Make sure that the change passes the CI checks.
ba356e5df7