helm: Support extending cilium-agent volume helm templates

Similar to hubble-relay, we want to repackage the cilium chart
and mount volumes based on additional helm values and templates.

To support adding new volumes, new template blocks ("partial")
have been added allowing downstream packagers to simplify modify
_extensions.tpl in their fork with the required logic.

Signed-off-by: Alexandre Barone <abalexandrebarone@gmail.com>

Author: devodev

install/kubernetes/cilium/templates/_extensions.tpl

@@ -3,6 +3,15 @@ _extensions.tpl contains template blocks that are intended to allow packagers
 to modify or extend the default chart behaviors.
 */}}
 
+{{/*
+Allow packagers to add extra volumes to cilium-agent.
+*/}}
+{{- define "cilium-agent.volumes.extra" }}
+{{- end }}
+
+{{- define "cilium-agent.volumeMounts.extra" }}
+{{- end }}
+
 {{/*
 Intentionally empty to allow downstream chart packagers to add extra
 containers to hubble-relay without having to modify the deployment manifest

install/kubernetes/cilium/templates/cilium-agent/daemonset.yaml

@@ -413,6 +413,7 @@ spec:
         {{- with .Values.extraVolumeMounts }}
         {{- toYaml . | nindent 8 }}
         {{- end }}
+        {{- include "cilium-agent.volumeMounts.extra" . | nindent 8 }}
       {{- if .Values.monitor.enabled }}
       - name: cilium-monitor
         image: {{ include "cilium.image" .Values.image | quote }}
@@ -1093,4 +1094,5 @@ spec:
       {{- with .Values.extraVolumes }}
       {{- toYaml . | nindent 6 }}
       {{- end }}
+      {{- include "cilium-agent.volumes.extra" . | nindent 6 }}
 {{- end }}