lifecycle add some guardrails and add docs

library/common-test/tests/container_in_deployment/lifecycle_test.yaml

@@ -148,6 +148,15 @@ tests:
                   - /bin/bash
                   - some_value
 
+  - it: should fail with invalid key
+    set:
+      lifecycle:
+        preStart:
+          command: something
+    asserts:
+      - failedTemplate:
+          errorMessage: Invalid key (preStart) in lifecycle. Valid keys are preStop and postStart
+
   - it: should fail with no command in preStop
     set:
       lifecycle:

library/common/1.0.0/templates/lib/container/_lifecycle.tpl

@@ -1,5 +1,12 @@
 {{/* Returns the lifecycle for the container */}}
 {{- define "ix.v1.common.container.lifecycle" -}}
+  {{- with .Values.lifecycle -}}
+    {{- range $k, $v := . -}}
+      {{- if not (has $k (list "preStop" "postStart")) -}}
+        {{- fail (printf "Invalid key (%s) in lifecycle. Valid keys are preStop and postStart" $k ) -}}
+      {{- end -}}
+    {{- end -}}
+  {{- end -}}
   {{- if (hasKey .Values.lifecycle "preStop") -}}
     {{- with .Values.lifecycle.preStop.command }}
       {{- print "preStop:" | nindent 0 }}

library/common/_docs/values/lifecycle.md

@@ -0,0 +1,75 @@
+# Lifecycle
+
+## Key: lifecycle
+
+- Type: `dict`
+- Default: `{}`
+- Helm Template:
+  - lifecycle.preStop.command - String: ✅
+  - lifecycle.preStop.command - List entry: ✅
+  - lifecycle.postStart.command - String: ✅
+  - lifecycle.postStart.command - List entry: ✅
+
+`lifecycle` key defines hooks that can run on the pod. Like `preStop` or `postStart`
+
+Examples `preStop`:
+
+```yaml
+# String / Single command
+lifecycle:
+  preStop:
+    command: ./custom-script.sh
+# String / Single command (tpl)
+lifecycle:
+  preStop:
+    command: "{{ .Values.customCommand }}"
+
+# List
+lifecycle:
+  preStop:
+    command:
+      - /bin/sh
+      - -c
+      - |
+        echo "Doing things..."
+# List (tpl)
+lifecycle:
+  preStop:
+    command:
+      - /path/to/executable
+      - --port
+      - "{{ .Values.service.main.ports.main.port }}"
+```
+
+Examples `postStart`:
+
+```yaml
+# String / Single command
+lifecycle:
+  postStart:
+    command: ./custom-script.sh
+# String / Single command (tpl)
+lifecycle:
+  postStart:
+    command: "{{ .Values.customCommand }}"
+
+# List
+lifecycle:
+  postStart:
+    command:
+      - /bin/sh
+      - -c
+      - |
+        echo "Doing things..."
+# List (tpl)
+lifecycle:
+  postStart:
+    command:
+      - /path/to/executable
+      - --port
+      - "{{ .Values.service.main.ports.main.port }}"
+```
+
+Kubernetes Documentation:
+
+- [lifecycle hooks](https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks)