[RHCLOUD-27862] add Pod Lifecyle hooks

[maskarb]

https://issues.redhat.com/browse/RHCLOUD-27862

minimal example (use the example clowdenv.yml):

apiVersion: cloud.redhat.com/v1alpha1
kind: ClowdApp
metadata:
  name: hello
  namespace: jumpstart
spec:
  envName: env-jumpstart
  deployments:
  - name: app
    podSpec:
      image: nginx
      terminationGracePeriodSeconds: 500
      lifecycle:
        postStart:
          exec:
            command:
            - "/bin/sh"
            - "-c"
            - echo "$(date -Iseconds) ...MESSAGE FROM THE POSTSTART HOOK..." > /proc/1/fd/1
        preStop:
          exec:
            command:
              - "/bin/sh"
              - "-c"
              - echo "$(date -Iseconds) ...MESSAGE FROM THE PRESTOP HOOK..." > /proc/1/fd/1
    webServices:
      private:
        enabled: true
      public:
        enabled: true

(These hooks are a variation from: https://thecloudblog.net/lab/kubernetes-container-lifecycle-events-and-hooks/. The echo "message" > /proc/1/fd/1 prints that message to the pod logs so we can see the hooks in action)

The deployment generated by this clowdapp contains:

...
          lifecycle:
            postStart:
              exec:
                command:
                  - /bin/sh
                  - '-c'
                  - echo "$(date -Iseconds) ...MESSAGE FROM THE POSTSTART HOOK..." > /proc/1/fd/1
            preStop:
              exec:
                command:
                  - /bin/sh
                  - '-c'
                  - echo "$(date -Iseconds) ...MESSAGE FROM THE PRESTOP HOOK..." > /proc/1/fd/1
          ...
      terminationGracePeriodSeconds: 500
...

Using this image and lifecycle hooks, open the pod terminal and see the printed log messages. The readiness/liveness probes will fail for this container. So when the pod restarts, we can see the preStop hook just before the sigquit was received:

2023/11/01 21:44:08 [notice] 1#1: start worker process 34
2023-11-01T21:44:08+00:00 ...MESSAGE FROM THE POSTSTART HOOK...
2023-11-01T21:45:37+00:00 ...MESSAGE FROM THE PRESTOP HOOK...
2023/11/01 21:45:37 [notice] 1#1: signal 3 (SIGQUIT) received, shutting down

[psav]

Can you run make pre-push on this please?

[maskarb]

Can you run make pre-push on this please?

Done!

I will note, I have not done any testing of these changes at all yet. I was going to see if I can get this working, and then see if yall had any thoughts on these changes to the Spec.

[psav]

I have no problem with the spec changes

[adamrdrew]

LGTM really, but a couple of questions before approval

[bsquizz]

Sorry just a couple minor doc generator things again

[bsquizz]

I'll sort out those doc generation shenanigans later, it doesn't need to hold up this PR

[psav]

Pending test outcome I'm happy to merge this

[psav]

/retest