service: Support validating templated files

roles/service/tasks/host_mounts.yaml

@@ -23,8 +23,16 @@
     src: "{{ item[0].source }}"
     dest: "{{ item[1] }}"
     mode: "{{ item[0].mode | default('0644') }}"
+    validate: "{{ validate if item[0].template_validate_command is defined else omit }}"
   notify: Restart container service {{ service_name }}
   loop: "{{ _service_all_template_mounts | zip(_service_all_template_mount_host_files) }}"
+  vars:
+    validate: >-
+      podman run --rm
+      -v %s:{{ item[0].destination }}:ro
+      --entrypoint {{ item[0].template_validate_command.split(' ', 1)[0] }}
+      {{ service_container_image }}
+      {{ item[0].template_validate_command.split(' ', 1)[1] }}
 
 - name: Copy files for copy mounts
   ansible.builtin.copy: