Network plugin custom (#9819)

* network_plugin/custom_cni: add CNI to apply provided manifests

Add a new simple custom_cni to install provided Kubernetes manifests.
This could be useful to use manifests directly provided by a CNI when
there are not support by Kubespray (i.e.: helm chart or any other manifests
generation method).

Co-authored-by: James Landrein <james.landrein@proton.ch>
Signed-off-by: Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@proton.ch>

* network_plugin/custom_cni: add test with cilium

Co-authored-by: James Landrein <james.landrein@proton.ch>
Signed-off-by: Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@proton.ch>

---------

Signed-off-by: Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@proton.ch>
Co-authored-by: James Landrein <james.landrein@proton.ch>

tests/files/custom_cni/README.md

@@ -0,0 +1,11 @@
+# Custom CNI manifest generation
+
+As an example we are using Cilium for testing the network_plugins/custom_cni.
+
+To update the generated manifests to the latest version do the following:
+
+```sh
+helm repo add cilium https://helm.cilium.io/
+helm repo update
+helm template cilium/cilium -n kube-system -f values.yaml > cilium.yaml
+```

tests/files/custom_cni/values.yaml

@@ -0,0 +1,11 @@
+---
+
+# We disable hubble so that helm doesn't try to generate any certificate.
+# This is not needed to test network_plugin/custom_cni anyway.
+hubble:
+  enabled: false
+
+ipam:
+  operator:
+    # Set the appropriate pods subnet
+    clusterPoolIPv4PodCIDR: "{{ kube_pods_subnet }}"

tests/files/packet_debian11-custom-cni.yml

@@ -0,0 +1,9 @@
+---
+# Instance settings
+cloud_image: debian-11
+mode: default
+
+# Kubespray settings
+kube_network_plugin: custom_cni
+custom_cni_manifests:
+  - tests/files/custom_cni/cilium.yaml