C8SM Zeebe REST API is left out of ingress installation guide

[jessesimpson36]

SUPPORT-23061

In the above ticket, the customer navigated to https://docs.camunda.io/docs/apis-tools/zeebe-api-rest/zeebe-api-rest-overview/

and was missing some key information regarding how to set up the zeebe rest api, and making requests against it.

While working on the ticket, the customer specifically asks:

1. Which service should be called ( kubernetes port-forward ) to access it?
2. Which URL should we use?

It should be noted somewhere that the service that provides the rest api is the zeebe gateway (in case customers have issues connecting to their ingress, they should be able to test via port-forwards). And perhaps there could be a link from above link to the self-managed documentation where we set up the ingress.

I also noticed that the "Combined and separated ingress setup" does not include the necessary options to enable the zeebe rest api.

a snippet like

zeebeGateway:
  contextPath: "/zeebe"
  ingress:
    grpc:
      enabled: true
      className: nginx
      host: "zeebe.camunda.example.com"
+    rest:
+      enabled: true
+      className: nginx
+      host: "camunda.example.com"
+      path: "/zeebe"

should be added.