Optionally write ca.crt to ConfigMap

[denniskniep]

Is your feature request related to a problem? Please describe.
If you need to specify a BackendTLSPolicy when using the GatewayAPI you need the ca.crt inside a ConfigMap.
See:

• https://gateway-api.sigs.k8s.io/api-types/backendtlspolicy/#cacertficaterefs
• https://gateway-api.sigs.k8s.io/guides/tls/#using-explicit-ca-certificates

Currently if you create a certificate, the ca.crt will be only created inside a secret.

Describe the solution you'd like
Would be nice, if you could also specify configMapName (optionally), next to the secretName inside the Kind:Certificate.
Result would be if specified, that a new ConfigMap is created with the appropriate ca.crt entry (for sure not including the private key!)

Furthermore is does make sense to also add configMapTemplate (same way as secretTemplate is defined).

/kind feature