Modified backup task to use the 'copy' module instead of 'shell' by p…

…assing the 'remote_src' option. This helps to enforce a desired state model and reduces ambiguity on success/failure.

tasks/main.yml

@@ -106,13 +106,12 @@
   when: __postfix_has_config_changed | d("") is search("True")
   block:
     - name: Backup configuration
-      shell: >-
-        set -euo pipefail;
-        cp /etc/postfix/main.cf
-        /etc/postfix/main.cf.{{ postfix_backup_multiple |
-        ternary("$(date -Iseconds)", "backup") }}
+      copy:
+        remote_src: yes
+        src: /etc/postfix/main.cf
+        dest: /etc/postfix/main.cf.{{ postfix_backup_multiple |
+          ternary(lookup('pipe', 'date -Iseconds'), "backup") }}
       when: postfix_backup or postfix_backup_multiple
-      changed_when: true
 
     - name: Ensure Last modified header is absent
       lineinfile: