docs: add comments explaining ingress class logic

{{/* We set the annotation value regardless of API versions, because the user may have an old controller that still works */}}

kubernetes.io/ingress.class: {{ .Values.ingress.className | default "nginx" | quote }}

{{- if .Values.ingress.tls.enabled }}

kubernetes.io/tls-acme: {{ .Values.ingress.tls.acme | quote }}

  annotations:

{{ include "ingress.annotations" . | indent 4 }}

spec:

{{/* We don't set a default value because old ingress controllers may not provide an IngressClass, causing deployments to fail */}}

{{- if and .Values.ingress.className (.Capabilities.APIVersions.Has "networking.k8s.io/v1/Ingress") }}

  ingressClassName: {{ .Values.ingress.className | quote }}

{{- end }}