docs: add section for generated code (#4465)

Signed-off-by: Charles-Edouard Brétéché <charled.breteche@gmail.com>

Signed-off-by: Charles-Edouard Brétéché <charled.breteche@gmail.com>

DEVELOPMENT.md

@@ -5,7 +5,6 @@ This document covers basic needs to work with Kyverno codebase.
 It contains instructions to build, run, and test Kyverno.
 
 - [Tools](#tools)
-- [Building and publishing an image locally](#building-and-publishing-an-image-locally)
 - [Building local binaries](#building-local-binaries)
 - [Building local images](#building-local-images)
     - [Building local images with docker](#building-local-images-with-docker)
@@ -17,6 +16,10 @@ It contains instructions to build, run, and test Kyverno.
     - [Create a local cluster](#create-a-local-cluster)
     - [Build and load local images](#build-and-load-local-images)
     - [Deploy with helm](#deploy-with-helm)
+- [Code generation](#code-generation)
+    - [Generating kubernetes API client](#generating-kubernetes-api-client)
+    - [Generating API deep copy functions](#generating-api-deep-copy-functions)
+    - [Generating CRD definitions](#generating-crd-definitions)
 
 ## Tools
 
@@ -348,6 +351,59 @@ This will build local images, load built images in every node of the KinD cluste
 
 You can override the KinD cluster name by setting the `KIND_NAME` environment variable (default value is `kind`).
 
+## Code generation
+
+We are using code generation tools to create the following portions of code:
+- [Generating kubernetes API client](#generating-kubernetes-api-client)
+- [Generating API deep copy functions](#generating-api-deep-copy-functions)
+- [Generating CRD definitions](#generating-crd-definitions)
+
+> **Note**: You can run `make codegen-all` to build all generated code at once.
+
+### Generating kubernetes API client
+
+TODO
+
+### Generating API deep copy functions
+
+Based on the [APIs golang code definitions](./api), you can generate the corresponding deep copy functions by running:
+```console
+# generate all deep copy functions
+make codegen-deepcopy-all
+```
+or
+```console
+# generate kyverno deep copy functions
+make codegen-deepcopy-kyverno
+```
+or
+```console
+# generate policy reports deep copy functions
+make codegen-deepcopy-report
+```
+
+This will output files named `zz_generated.deepcopy.go` in every API package.
+
+### Generating CRD definitions
+
+Based on the [APIs golang code definitions](./api), you can generate the corresponding CRDs manifests by running:
+```console
+# generate all CRDs
+make codegen-crds-all
+```
+or
+```console
+# generate Kyverno CRDs
+make codegen-crds-kyverno
+```
+or
+```console
+# generate policy reports CRDs
+make codegen-crds-report
+```
+
+This will output CRDs manifests [/config/crds](./config/crds).
+
 ## Building and publishing an image locally
 
 First, make sure you [install `ko`](https://github.com/google/ko#install)

Makefile

@@ -283,6 +283,35 @@ docker-publish-all: docker-publish-kyvernopre docker-publish-kyverno docker-publ
 .PHONY: docker-publish-all-dev
 docker-publish-all-dev: docker-publish-kyvernopre-dev docker-publish-kyverno-dev docker-publish-cli-dev
 
+###########
+# CODEGEN #
+###########
+
+.PHONY: codegen-crds-kyverno
+codegen-crds-kyverno: $(CONTROLLER_GEN) ## Generate Kyverno CRDs
+	@$(CONTROLLER_GEN) crd paths=./api/kyverno/... crd:crdVersions=v1 output:dir=./config/crds
+
+.PHONY: codegen-crds-report
+codegen-crds-report: $(CONTROLLER_GEN) ## Generate policy reports CRDs
+	@$(CONTROLLER_GEN) crd paths=./api/policyreport/... crd:crdVersions=v1 output:dir=./config/crds
+
+.PHONY: codegen-crds-all
+codegen-crds-all: codegen-crds-kyverno codegen-crds-report ## Generate all CRDs
+
+.PHONY: codegen-deepcopy-kyverno
+codegen-deepcopy-kyverno: $(CONTROLLER_GEN) $(GOIMPORTS) ## Generate Kyverno deep copy functions
+	@$(CONTROLLER_GEN) object:headerFile="scripts/boilerplate.go.txt" paths="./api/kyverno/..." && $(GOIMPORTS) -w ./api/kyverno
+
+.PHONY: codegen-deepcopy-report
+codegen-deepcopy-report: $(CONTROLLER_GEN) $(GOIMPORTS) ## Generate policy reports deep copy functions
+	@$(CONTROLLER_GEN) object:headerFile="scripts/boilerplate.go.txt" paths="./api/policyreport/..." && $(GOIMPORTS) -w ./api/policyreport
+
+.PHONY: codegen-deepcopy-all
+codegen-deepcopy-all: codegen-deepcopy-kyverno codegen-deepcopy-report ## Generate all deep copy functions
+
+.PHONY: codegen-all
+codegen-all: codegen-deepcopy-all codegen-crds-all ## Generate all CRDs and deep copy functions
+
 ##################################
 # KYVERNO
 ##################################