Refactor services-to-host-mapping and playbooks

roles/backup/vars/main.yml

@@ -5,7 +5,8 @@ backup_image: "{{ (container_registry.public, 'services/backup') | path_join }}"
 backup_svc:
   name: backup
 
-backup_volumes_service: "{{ host_backup.volumes | map_backup_volumes_service }}"
+backup_volumes_list: "{{ all_services | my_service_attributes(host_services, 'volumes_backup') }}"
+backup_volumes_service: "{{ backup_volumes_list | map_backup_volumes_service }}"
 
 backup_env:
   HC_UID: "{{ host_backup.hc_uid }}"
@@ -56,4 +57,4 @@ backup_compose:
         devices:
           - /dev/fuse
 
-    volumes: "{{ host_backup.volumes | map_backup_volumes }}"
+    volumes: "{{ backup_volumes_list | map_backup_volumes }}"