service: Validation, set default for mounts in additional containers

roles/service/tasks/validation.yaml

@@ -1,4 +1,9 @@
 ---
+- name: Fail if service_name is empty
+  ansible.builtin.fail:
+    msg: service_name must not be empty
+  when: service_name | length == 0
+
 - name: Fail if service_container_user is not string
   ansible.builtin.fail:
     msg: "service_container_user must be a string, not int."

roles/service/vars/main/mounts.yaml

@@ -45,7 +45,7 @@ _service_all_template_mounts: >-
       _service_template_mounts +
       (
         _service_additional_containers |
-        map(attribute='mounts') |
+        map(attribute='mounts', default=[]) |
         flatten
       )
     ) |