feat(restic): Add restic backup maintenance stack

Sets up regular backup maintenance for a restic (S3) backend, and
enables global variables for other roles to use for their individual
backup. Example found in nextcloud role.

roles/nextcloud/templates/docker-stack.yml.j2

@@ -160,24 +160,22 @@ services:
     networks:
       - backend
 
-{% if nextcloud_backup_db_enable is not undefined and not false %}
+{% if backup_enable is not undefined and not false and nextcloud_backup_enable is not undefined and not false %}
   backup:
     image: mazzolino/restic
     environment:
-      - "TZ={{ nextcloud_backup_db_timezone }}"
+      - "TZ={{ restic_timezone }}"
        # go-cron starts w seconds
-      - "BACKUP_CRON=0 30 3 * * *"
-      - "RESTIC_REPOSITORY={{ nextcloud_backup_db_repo }}"
-      - "AWS_ACCESS_KEY_ID={{ nextcloud_backup_db_key }}"
-      - "AWS_SECRET_ACCESS_KEY={{ nextcloud_backup_db_secret }}"
-      - "RESTIC_PASSWORD={{ nextcloud_backup_db_pass }}"
-      - "RESTIC_BACKUP_TAGS=nextcloud-db"
-      - "RESTIC_BACKUP_SOURCES=/mnt/volumes"
+      - "BACKUP_CRON={{ nextcloud_backup_cron }}"
+      - "RESTIC_REPOSITORY={{ restic_repo }}"
+      - "AWS_ACCESS_KEY_ID={{ restic_s3_key }}"
+      - "AWS_SECRET_ACCESS_KEY={{ restic_s3_secret }}"
+      - "RESTIC_PASSWORD={{ restic_pass }}"
+      - "RESTIC_BACKUP_TAGS=nextcloud"
+      - "RESTIC_BACKUP_SOURCES=/volumes"
     volumes:
-      - db:/mnt/volumes/nextcloud_db:ro
-      - data:/mnt/volumes/nextcloud_data:ro
-    networks:
-      - backend
+      - db:/volumes/nextcloud_db:ro
+      - data:/volumes/nextcloud_data:ro
 {% endif %}
 
   # metrics: