Webhook configuration is fairly limited

[raz-bn]

Currently, it is only possible to generate a webhook manifest for a service running inside the cluster. However, I think it should also be possible to generate manifests for webhook running outside the cluster by providing the Validating/MutatingWebhookConfiguration with a URL instead of a service.
This use case can be handy when trying to run a local webhook while developing one.
I order to achieve this with the current controller-gen, you need to this manual changes:

1. Edit webhook/manifests.yaml and replace Service with the desired URL:

 ---
apiVersion: admissionregistration.k8s.io/v1beta1
kind: ValidatingWebhookConfiguration
metadata:
  creationTimestamp: null
  name: validating-webhook-configuration
webhooks:
- clientConfig:
    caBundle: Cg==
    url: https://example.com/validate
  failurePolicy: Fail
  name: exa.mple.com
  rules:
  - apiGroups:
    - ""
    apiVersions:
    - v1
    operations:
    - DELETE
    resources:
    - namespaces

2. Edit webhook/kustomization.yaml and comment those lines:

resources:
- manifests. yaml
#- service.yaml

configurations:
#- kustomizeconfig.yaml

3. Edit certmanager/certificate.yaml and add the DNS name:

# The following manifests contain a self-signed issuer CR and a certificate CR.
# More document can be found at https://docs.cert-manager.io
# WARNING: Targets CertManager 0.11 check https://docs.cert-manager.io/en/latest/tasks/upgrading/index.html for 
# breaking changes
apiVersion: cert-manager.io/v1alpha2
kind: Issuer
metadata:
  name: selfsigned-issuer
  namespace: system
spec:
  selfSigned: {}
---
apiVersion: cert-manager.io/v1alpha2
kind: Certificate
metadata:
  name: serving-cert  # this name should match the one appeared in kustomizeconfig.yaml
  namespace: system
spec:
  # $(SERVICE_NAME) and $(SERVICE_NAMESPACE) will be substituted by kustomize
  dnsNames:
  - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc
  - $(SERVICE_NAME).$(SERVICE_NAMESPACE).svc.cluster.local
  - example.com
  issuerRef:
    kind: Issuer
    name: selfsigned-issuer
  secretName: webhook-server-cert # this secret will not be prefixed, since it's not managed by kustomize

4. Edit default/kustomization.yaml and comment SERVICE_NAMESPACE and SERVICE_NAME variables:

# Adds namespace to all resources.
namespace: sns-system

# Value of this field is prepended to the
# names of all resources, e.g. a deployment named
# "wordpress" becomes "alices-wordpress".
# Note that it should also match with the prefix (text before '-') of the namespace
# field above.
namePrefix: sns-

# Labels to add to all resources and selectors.
#commonLabels:
#  someName: someValue

bases:
- ../crd
- ../rbac
- ../manager
# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in 
# crd/kustomization.yaml
- ../webhook
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'. 'WEBHOOK' components are required.
- ../certmanager
# [PROMETHEUS] To enable prometheus monitor, uncomment all sections with 'PROMETHEUS'. 
#- ../prometheus

patchesStrategicMerge:
  # Protect the /metrics endpoint by putting it behind auth.
  # If you want your controller-manager to expose the /metrics
  # endpoint w/o any authn/z, please comment the following line.
- manager_auth_proxy_patch.yaml

# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in 
# crd/kustomization.yaml
- manager_webhook_patch.yaml

# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'.
# Uncomment 'CERTMANAGER' sections in crd/kustomization.yaml to enable the CA injection in the admission webhooks.
# 'CERTMANAGER' needs to be enabled to use ca injection
- webhookcainjection_patch.yaml

# the following config is for teaching kustomize how to do var substitution
vars:
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER' prefix.
- name: CERTIFICATE_NAMESPACE # namespace of the certificate CR
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
  fieldref:
    fieldpath: metadata.namespace
- name: CERTIFICATE_NAME
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
#- name: SERVICE_NAMESPACE # namespace of the service
#  objref:
#    kind: Service
#   version: v1
#    name: webhook-service
#  fieldref:
#    fieldpath: metadata.namespace
#- name: SERVICE_NAME
#  objref:
#    kind: Service
#    version: v1
#    name: webhook-service

[fejta-bot]

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/lifecycle stale

[fejta-bot]

Stale issues rot after 30d of inactivity.
Mark the issue as fresh with /remove-lifecycle rotten.
Rotten issues close after an additional 30d of inactivity.

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/lifecycle rotten

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Reopen the issue with /reopen.
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/close

[k8s-ci-robot]

@fejta-bot: Closing this issue.

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Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

Send feedback to sig-contributor-experience at kubernetes/community.
/close

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[rikatz]

/reopen

[k8s-ci-robot]

@rikatz: Reopened this issue.

In response to this:

/reopen

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[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
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• Mark this issue as fresh with /remove-lifecycle rotten
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/close not-planned

[k8s-ci-robot]

@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Reopen this issue with /reopen
• Mark this issue as fresh with /remove-lifecycle rotten
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/close not-planned

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[sbueringer]

/reopen
/remove-lifecycle rotten
/lifecycle active

[k8s-triage-robot]

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This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Mark this issue as fresh with /remove-lifecycle stale
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• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues.

This bot triages un-triaged issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

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• Offer to help out with Issue Triage

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/lifecycle rotten

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

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• Mark this issue as fresh with /remove-lifecycle rotten
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/close not-planned

[k8s-ci-robot]

@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

You can:

• Reopen this issue with /reopen
• Mark this issue as fresh with /remove-lifecycle rotten
• Offer to help out with Issue Triage

Please send feedback to sig-contributor-experience at kubernetes/community.

/close not-planned

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[sbueringer]

This was fixed in #824

[sbueringer]

/close

[k8s-ci-robot]

@sbueringer: Closing this issue.

In response to this:

/close

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