Allow Pomerium CRD to have global annotations to be used for every ingress

[bennesp]

Is your feature request related to a problem? Please describe.

In my cluster, I would like to apply some configurations to every Ingress that Pomerium ingress-controller manages.

As an example, I would like to be able to configure ingress.pomerium.io/preserve_host_header: true to every Ingress, so that every Service receives the HTTP request with the original Host header.

Describe the solution you'd like

I thought of mainly two solutions:

• A generic one: modify the Pomerium CRD to support a .spec.ingressAnnotations or .spec.annotations or similar field. This field would be of type map[string]string. While evaluating every Ingress, the Pomerium ingress-controller would first merge the global annotations defined in the Pomerium CRD in the new field with the Ingress specific ones, and then proceed in the evaluation of the Ingress
• A specific one: create a new field in Pomerium CRD for every configuration. In the above example, I would expect a .spec.preserveHostHeader bool field to exist

Explain any additional use-cases

The generic approach would be beneficial for many other annotations that do not have a global setting right now