tetragon-oci-hook: developer demo

Add a developer demo. We will move this to docuemntation proper once the
PR is merged, and the image is updated.

Signed-off-by: Kornilios Kourtis <[email protected]>

contrib/rthooks/tetragon-oci-hook/docs/demo.md

@@ -0,0 +1,63 @@
+This is a dev demo of how to install the teragon OCI hook on a CRI-O runtime.
+
+Note: we should move this to the documentation once the PR is merged and `tetragon-oci-hook` and
+`tetragon-oci-hook-setup` are part of the tetragon development image.
+
+
+Start minikube:
+
+```shell-session
+minikube start --driver=kvm2 --container-runtime=cri-o
+```
+
+Build images and load them to minikube:
+
+```shell-session
+make image image-operator
+minikube image load cilium/tetragon:latest
+minikube image load cilium/tetragon-operator:latest
+minikube image list | grep tetragon
+localhost/cilium/tetragon:latest
+localhost/cilium/tetragon-operator:latest
+```
+
+Install the image enabling the init container:
+
+```
+helm install --namespace kube-system \
+        --set tetragonOperator.image.override=localhost/cilium/tetragon-operator:latest \
+        --set tetragon.image.override=localhost/cilium/tetragon:latest  \
+        --set tetragon.grpc.address="unix:///var/run/cilium/tetragon/tetragon.sock" \
+        --set tetragon.ociHookSetup.enabled=true \
+        tetragon ./install/kubernetes
+...
+kubectl logs -n kube-system tetragon-289tf  -c oci-hook-setup
+time="2023-12-05T09:28:50Z" level=info msg="written binary" hook-dst-path=/hostInstall/tetragon-oci-hook
+time="2023-12-05T09:28:50Z" level=info msg="written conf" conf-dst-path=/hostHooks/tetragon-oci-hook.json
+```
+
+Check the hook looks:
+```
+minikube ssh -- tail -f /opt/tetragon/tetragon-oci-hook.log 
+...
+time="2023-12-05T09:31:08Z" level=info msg="hook request to agent succeeded" hook=create-container ...
+```
+
+You can now uninstall tetragon:
+```
+helm uninstall -n kube-system tetragon
+```
+
+In many situations, you would want the hook to keep running even if tetragon is
+not. Doing so, will allow you to configure a class of pods that can only run if tetragon is availble.
+
+
+To uninstall the hook, you can install the following daemonset:
+```
+kubectl -n  kube-system  apply -f contrib/rthooks/tetragon-oci-hook/k8s/ds-uninstall.yaml
+kubectl -n kube-system logs tetragon-oci-hook-uninstall-8t4bl -c setup
+time="2023-12-05T09:37:37Z" level=info msg="conf removed" conf-dst-path=/hostHooks/tetragon-oci-hook.json error="<nil>"
+time="2023-12-05T09:37:37Z" level=info msg="binary removed" bin-dst-path=/hostInstall/tetragon-oci-hook error="<nil>"
+```
+
+(NB: above is not ideal, we should find a better way to do this)