feat: add pre-defined secrets to csi-driver-smb addon (#1215)

* added ability to use pre-defined secrets

* renamed variables to existing_secret_name and existing_secret_namespace

bootstrap/templates/kubernetes/apps/storage/csi-driver-smb/app/secrets.sops.yaml.j2

@@ -1,5 +1,6 @@
 #% if csi_driver_smb|default({}) and csi_driver_smb.enabled|default(false) %#
 #% for item in csi_driver_smb.storage_class %#
+#% if not item.existing_secret_name %#
 ---
 apiVersion: v1
 kind: Secret
@@ -8,5 +9,6 @@ metadata:
 stringData:
   username: "#{ item.username }#"
   password: "#{ item.password }#"
+#% endif %#
 #% endfor %#
 #% endif %#