⚠️ (go/v4) decouple webhooks from APIs - Move Webhooks from `api/<ver…

…sion>` or `api/<group>/<version>` to `internal/webhook/<version>` or `internal/webhook/<group>/<version>`

This PR decouples the webhooks from the API, aligning with the recent breaking changes introduced in controller-runtime to ensure that kubebuilder still compatbile with its next release.  Webhooks are now scaffolded under `internal/webhook` to comply with the latest standards.

**Context:**

Controller-runtime deprecated and removed the webhook methods in favor of CustomInterfaces (see [controller-runtime#2641](kubernetes-sigs/controller-runtime#2641)). The motivation for this change is outlined in [controller-runtime#2596](kubernetes-sigs/controller-runtime#2596).

See that the current master branch already reflects these changes, using the CustomInterfaces: [kubebuilder#4060](kubernetes-sigs#4060).

**Changes:**

- Webhooks are now scaffolded in `internal/webhook/<version>` or `internal/webhook/<group>/<version>`.
- However, to ensure backwards compatibility, a new `--legacy` flag is introduced. Running `kubebuilder create webhook [options] --legacy` will scaffold webhooks in the legacy location for projects that need to retain the old structure. However, users will still to address the breaking changes in the source code by replacing the old methods by the new CustomInterfaces.

.github/workflows/legacy-webhook-path.yml

@@ -0,0 +1,32 @@
+# This test ensure that the legacy webhook path
+# still working. The option is deprecated
+# and should be removed when we no longer need
+# to support go/v4 plugin.
+name: Legacy Webhook Path
+
+on:
+  push:
+    paths:
+      - 'testdata/**'
+      - '.github/workflows/legacy-webhook-path.yml'
+  pull_request:
+    paths:
+      - 'testdata/**'
+      - '.github/workflows/legacy-webhook-path.yml'
+
+jobs:
+  webhook-legacy-path:
+    name: Verify Legacy Webhook Path
+    runs-on: ubuntu-latest
+    # Pull requests from the same repository won't trigger this checks as they were already triggered by the push
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
+    steps:
+      - name: Clone the code
+        uses: actions/checkout@v4
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.22.3'
+      - name: Run make test-legacy
+        run: make test-legacy
+

.gitignore

@@ -25,4 +25,5 @@ docs/book/src/docs
 # skip testdata go.sum, since it may have
 # different result depending on go version
 /testdata/**/go.sum
-/docs/book/src/simple-external-plugin-tutorial/testdata/sampleexternalplugin/v1/bin
+/docs/book/src/simple-external-plugin-tutorial/testdata/sampleexternalplugin/v1/bin
+/testdata/**legacy**

Makefile

@@ -164,3 +164,10 @@ test-license:  ## Run the license check
 .PHONY: test-spaces
 test-spaces:  ## Run the trailing spaces check
 	./test/check_spaces.sh
+
+## TODO: Remove me when go/v4 plugin be removed
+## Deprecated
+.PHONY: test-legacy
+test-legacy:  ## Run the tests to validate legacy path for webhooks
+	rm -rf  ./testdata/**legacy**/
+	./test/testdata/legacy-webhook-path.sh

docs/book/src/cronjob-tutorial/testdata/project/Dockerfile

@@ -14,7 +14,7 @@ RUN go mod download
 # Copy the go source
 COPY cmd/main.go cmd/main.go
 COPY api/ api/
-COPY internal/controller/ internal/controller/
+COPY internal/ internal/
 
 # Build
 # the GOARCH has not a default value to allow the binary be built according to the host where the command

docs/book/src/cronjob-tutorial/testdata/project/cmd/main.go

@@ -38,6 +38,7 @@ import (
 
 	batchv1 "tutorial.kubebuilder.io/project/api/v1"
 	"tutorial.kubebuilder.io/project/internal/controller"
+	webhookbatchv1 "tutorial.kubebuilder.io/project/internal/webhook/v1"
 	// +kubebuilder:scaffold:imports
 )
 
@@ -183,7 +184,7 @@ func main() {
 	*/
 	// nolint:goconst
 	if os.Getenv("ENABLE_WEBHOOKS") != "false" {
-		if err = (&batchv1.CronJob{}).SetupWebhookWithManager(mgr); err != nil {
+		if err = webhookbatchv1.SetupCronJobWebhookWithManager(mgr); err != nil {
 			setupLog.Error(err, "unable to create webhook", "webhook", "CronJob")
 			os.Exit(1)
 		}