feat(api): add ExternalHost property for routes

[ebaron]

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---

Fixes: #726

Description of the change:

• Adds spec.networkOptions.coreConfig.externalHost to the Cryostat v1beta2 CRD.
• Route spec.host is immutable once created. I had considered some logic to recreate the route if the user attempts to change the host in the CR, but this is further complicated due to OpenShift modifying the spec.host field in the default case where it dynamically assigns a hostname. I think trying to accommodate this is too risky for 3.0.

Motivation for the change:

• Allows users to specify a custom hostname for the Cryostat route on OpenShift

How to manually test:

1. Create a Cryostat CR with spec.networkOptions.coreConfig.externalHost defined to a custom value.

[andrewazores]

Looks good. I tested creating a CR without the new property and I got the old behaviour. Then I tried this CR:

apiVersion: v1
items:
- apiVersion: operator.cryostat.io/v1beta2
  kind: Cryostat
  metadata:
    creationTimestamp: "2024-06-07T19:40:32Z"
    finalizers:
    - operator.cryostat.io/cryostat.finalizer
    generation: 1
    name: cryostat-sample
    namespace: cryostat3
    resourceVersion: "201366"
    uid: f3abec79-1dec-41bb-b070-b3e596ffea60
  spec:
    enableCertManager: true
    networkOptions:
      coreConfig:
        externalHost: cryostat.example.com
    reportOptions:
      resources: {}
    storageOptions:
      pvc:
        spec:
          resources: {}
    targetNamespaces:
    - cryostat3
kind: List
metadata:
  resourceVersion: ""

and the result:

$ oc get route
NAME              HOST/PORT              PATH   SERVICES          PORT   TERMINATION          WILDCARD
cryostat-sample   cryostat.example.com          cryostat-sample   4180   reencrypt/Redirect   None