cert-manager should not be a hard requirement

[benmoss]

Is your feature request related to a problem? Please describe.
As an operator I'd prefer not to have to install cert-manager if I'm not trying to do anything fancy with certificate management.

Describe the solution you'd like
A documented way for users to bring their own certificates, but not necessarily via cert-manager.

Additional context
Strimzi is a comparable operator for managing Kafka clusters. They do not have a dependency on cert-manager and this is their documentation for how to manage your own certificates.

It seems like it automatically can provision its own certificates, but in the case of bring-your-own it just expects the user to provide Kubernetes secrets containing the certificates and keys. A user could use cert-manager to create these and still get the benefits of cert-manager, or whatever certificate management system they want.

[ChunyiLyu]

Hi @benmoss, I'm going to convert this issue to a github discussion because it seems to be more of a question 😄