K8s: fix standalone command and add hack scripts (#79052)

Co-authored-by: Charandas Batra <charandas.batra@grafana.com>

hack/README.md

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+# Kubernetes HACK Alert
+
+This is a hack folder for kubernetes codegen scripts. Oddly, a /hack/ folder seems to be standard kubernetes development practice ¯\_(ツ)\_/¯
+
+The workflow is a WIP, however we are trying to leverage as many off-the-shelf patterns as possible.
+
+For these scripts to work, your local GOROOT/src/grafana/grafana must point to this git checkout. For my setup this is:
+
+```
+❯ pwd
+/Users/ryan/go/src/github.com/grafana
+❯ ls -l
+total 0
+lrwxr-xr-x  1 ryan  staff  37 Oct  5 09:34 grafana -> /Users/ryan/workspace/grafana/grafana
+```
+
+The current workflow (sorry!) is to:
+
+1. update the script to point to the group+version you want
+2. run the `update-codegen.sh` script. This will produce a bunch of new files
+3. move `pkg/generated/openapi/zz_generated.openapi.go` to `pkg/apis/{group/version}/zz_generated.openapi.go`.
+4. edit the package name so it is {version} and remove the boilerplate k8s kinds
+5. `rm -rf pkg/generated` -- we are not yet using most of the generated client stuff
+
+Once we are more comfortable with the outputs and process, we will build these steps into a more standard codegen pattern, but until then... happy hacking!

hack/boilerplate.go.txt

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+// SPDX-License-Identifier: AGPL-3.0-only
+

hack/update-codegen.sh

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+#!/usr/bin/env bash
+
+# Copyright 2017 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+SCRIPT_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
+CODEGEN_PKG=${CODEGEN_PKG:-$(cd "${SCRIPT_ROOT}"; ls -d -1 ./vendor/k8s.io/code-generator 2>/dev/null || echo $GOPATH/pkg/mod/k8s.io/code-generator@v0.27.1)}
+
+OUTDIR="${HOME}/go/src"
+
+echo $OUTDIR
+
+CLIENTSET_NAME_VERSIONED=clientset \
+CLIENTSET_PKG_NAME=clientset \
+"${CODEGEN_PKG}/generate-groups.sh" "all" \
+  github.com/grafana/grafana/pkg/generated \
+  github.com/grafana/grafana/pkg/apis \
+  "snapshots:v0alpha1" \
+  --output-base "${OUTDIR}" \
+  --go-header-file "${SCRIPT_ROOT}/hack/boilerplate.go.txt"
+
+CLIENTSET_NAME_VERSIONED=clientset \
+CLIENTSET_PKG_NAME=clientset \
+"${CODEGEN_PKG}/generate-internal-groups.sh" "deepcopy,defaulter,conversion,openapi"  \
+  github.com/grafana/grafana/pkg/generated \
+  github.com/grafana/grafana/pkg/apis \
+  github.com/grafana/grafana/pkg/apis \
+  "snapshots:v0alpha1" \
+  --output-base "${OUTDIR}" \
+  --go-header-file "${SCRIPT_ROOT}/hack/boilerplate.go.txt"