Allow using a ClusterIssuer on the cluster for TLS #226
Description
Currently, the docs for ingress and TLS setup: https://github.com/developmentseed/eoapi-k8s/blob/main/docs/unified-ingress.md#configuration say to pass in the certManager issuer. However this issuer needs to be an Issuer resource in the same namespace, that can be a bit awkward to create separately.
One should be able to use a ClusterIssuer that's already installed on the cluster to provision TLS certificates.
For now, I'm working around by setting certManager to false and adding the custom annotation for the cluster issuer as annotations.