docs(cloudnativepg_operator): add upgrade runbook

ref: #15 #13 infrastructure/argo#3

Author: jon-nfc

manifests/cloudnativepg-operator/README.md

@@ -0,0 +1,45 @@
+# CloudnativePG Operator Kustomize
+
+
+## Upgrading manifests
+
+1. Fetch new release manifest
+
+    - Navigate to repository https://github.com/cloudnative-pg/cloudnative-pg
+
+    - Go To `releases` directory
+
+    - Change the branch to the desired tag _Tag sgould match the desired release_
+
+    - click on the file that matches the release version
+
+    - copy the permalink raw URL
+
+        Keep a copy of this url so it can be added to the commit message. Doing this will allow validity checking if required.
+
+1. split the manifest
+
+    From the apps dir `manifests/<app name>` run:
+
+    ``` bash
+
+    docker run -ti \
+      -e "KUBECTL_SLICE_INPUT_FILE=<Raw URL of manifest>" \
+      -e "KUBECTL_SLICE_OUTPUT_DIR=base/" \
+      -v manifests/cloudnativepg-operator:/workdir \
+      --rm \
+      nofusscomputing/kubernetes-manifest-tools:latest
+
+    ```
+
+1. update the Base kustomization
+
+    From the apps dir `manifests/<app name>` run:
+
+    ``` bash
+
+    ansible-playbook ../../../../other/kubernetes-manifest-tools/collection/playbooks/update-kustomize.yaml \
+      --extra-vars "namespace=operators" \
+      --extra-vars "manifest_dir=${PWD}/base"
+
+    ```