Allow additional preseed overrides

Sometimes the ephemeral environment needs additional cloud-init data.
This change allows user-data sections to be added to the default files
in /etc/maas/preseeds: enlist, commissioning, and curtin.

For example, to resolve issues with 'apt-get update' failures during
enlistment, something like this may be necessary:
conf:
  cloudconfig:
    override: true
    sections:
      bootcmd:
        - "rm -fr /var/lib/apt/lists"

Change-Id: I817006a799003ace3f35d02507489720b0f9079b

charts/maas/templates/configmap-etc.yaml

@@ -52,3 +52,11 @@ data:
 {{ tuple "etc/_logrotate.conf.tpl" . | include "helm-toolkit.utils.template" | indent 4 }}
   logrotate.cron: |
 {{ tuple "etc/_logrotate.cron.tpl" . | include "helm-toolkit.utils.template" | indent 4 }}
+{{- if .Values.conf.cloudconfig.override }}
+  enlist: |+
+{{ tuple "etc/_enlist.tpl" . | include "helm-toolkit.utils.template" | indent 4 }}
+  commissioning: |+
+{{ tuple "etc/_commissioning.tpl" . | include "helm-toolkit.utils.template" | indent 4 }}
+  curtin: |+
+{{ tuple "etc/_curtin.tpl" . | include "helm-toolkit.utils.template" | indent 4 }}
+{{- end }}

charts/maas/templates/etc/_commissioning.tpl

@@ -0,0 +1,4 @@
+{{ "{{" }}preseed_data{{ "}}" }}
+{{- range $k, $v := .Values.conf.cloudconfig.sections }}
+{{ dict $k $v | toYaml | trim }}
+{{- end }}

charts/maas/templates/etc/_curtin.tpl

@@ -0,0 +1,4 @@
+{{ "{{" }}preseed_data{{ "}}" }}
+{{- range $k, $v := .Values.conf.cloudconfig.sections }}
+{{ dict $k $v | toYaml | trim }}
+{{- end }}

charts/maas/templates/etc/_enlist.tpl

@@ -0,0 +1,13 @@
+#cloud-config
+datasource:
+  MAAS:
+    timeout : 50
+    max_wait : 120
+    # there are no default values for metadata_url or oauth credentials
+    # If no credentials are present, non-authed attempts will be made.
+    metadata_url: {{ "{{" }}metadata_enlist_url{{ "}}" }}
+
+output: {all: '| tee -a /var/log/cloud-init-output.log'}
+{{- range $k, $v := .Values.conf.cloudconfig.sections }}
+{{ dict $k $v | toYaml | trim }}
+{{- end }}

charts/maas/templates/statefulset-region.yaml

@@ -155,6 +155,20 @@ spec:
               subPath: ntpd.sh
               readOnly: true
 {{- end }}
+{{- if .Values.conf.cloudconfig.override }}
+            - name: maas-etc
+              mountPath: /etc/maas/preseeds/enlist
+              subPath: enlist
+              readOnly: true
+            - name: maas-etc
+              mountPath: /etc/maas/preseeds/commissioning
+              subPath: commissioning
+              readOnly: true
+            - name: maas-etc
+              mountPath: /etc/maas/preseeds/curtin
+              subPath: curtin
+              readOnly: true
+{{- end }}
 {{- if $mounts_maas_region.volumeMounts }}{{ toYaml $mounts_maas_region.volumeMounts | indent 12 }}{{ end }}
       volumes:
         - name: host-sys-fs-cgroup

charts/maas/values.yaml

@@ -192,6 +192,21 @@ conf:
     # Example:
     # late_commands:
     #   install_modules_extra: ["curtin", "in-target", "--", "apt-get", "-y", "install", "linux-modules-extra-4.15.0-88-generic"]
+  cloudconfig:
+    override: false
+    sections: {}
+    # Additional user-data sections to add to the default cloud-config.
+    # These apply to the ephemeral environment, used during enlistment,
+    # commissioning, and deployment (pre-curtin).
+    # In particular, bootcmd may be useful:
+    # https://cloudinit.readthedocs.io/en/latest/topics/modules.html#bootcmd
+    # Example:
+    # conf:
+    #   cloudconfig:
+    #     override: true
+    #     sections:
+    #       bootcmd:
+    #         - "rm -fr /var/lib/apt/lists"
   drydock:
     bootaction_url: null
   cache: