Allow extraManifests to be specified

[wasurerarenai]

Talos v1.7 now requires ExtensionServiceConfig's defined for configuring System Extensions (ex. nut-config). Talhelper added support for these in budimanjojo/talhelper#431, but including these in config.yaml looks like it could get pretty messy.

The node.extraManifests object supports including external files and works for including these needed configs. This patch adds parsing of the bootstrap_node_inventory[].manifests key to allow these to be included.

Example config.yaml

bootstrap_node_inventory:
  - name: node1
...
    manifests:
      - manifests/nut-config.yaml

Results in:

$ talhelper genconfig -dn
...
+++ b/.../home-kubernetes-node1.yaml
...
   allowSchedulingOnControlPlanes: true
+---
+apiVersion: v1alpha1
+kind: ExtensionServiceConfig
+name: nut-client
+configFiles:
+  - content: |-
+        MONITOR ${upsmonUpsName}@${upsmonHost}:${upsmonPort} 1 ${upsmonUser} ${upsmonPasswd} slave                                                                                                              +        SHUTDOWNCMD "/sbin/poweroff"
+    mountPath: /usr/local/etc/nut/upsmon.conf

with the manifests/nut-config.yaml content of:

apiVersion: v1alpha1
kind: ExtensionServiceConfig
name: nut-client
configFiles:
  - content: |-
        MONITOR ${upsmonUpsName}@${upsmonHost}:${upsmonPort} 1 ${upsmonUser} ${upsmonPasswd} slave
        SHUTDOWNCMD "/sbin/poweroff"
    mountPath: /usr/local/etc/nut/upsmon.conf