feat: add support for cluster user secrets and settings (#858)

Co-authored-by: Devin Buhl <onedr0p@users.noreply.github.com>
Co-authored-by: Devin Buhl <devin@buhl.casa>

bootstrap/templates/kubernetes/flux/vars/cluster-secrets-user.sops.yaml.j2

@@ -0,0 +1,8 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: cluster-secrets-user
+  namespace: flux-system
+stringData:
+  SECRET_PLACEHOLDER: "secret-value"