refactor(users): change system.users from list to dict keyed by username

roles/global_defaults/tasks/_validate_input.yml

@@ -25,17 +25,17 @@
     quiet: true
 
 - name: Validate system.users entries
-  when: system.users is defined and system.users | length > 0
+  when: system.users is defined and system.users is mapping and system.users | length > 0
   ansible.builtin.assert:
     that:
-      - item is mapping
-      - item.name is defined and (item.name | string | length) > 0
-      - item['keys'] is not defined or (item['keys'] is iterable and item['keys'] is not string)
-    fail_msg: "Each system.users[] entry must be a dict with 'name'; 'keys' must be a list."
+      - item.value is mapping
+      - item.key | string | length > 0
+      - item.value['keys'] is not defined or (item.value['keys'] is iterable and item.value['keys'] is not string)
+    fail_msg: "Each system.users entry must be a dict keyed by username; 'keys' must be a list."
     quiet: true
-  loop: "{{ system.users }}"
+  loop: "{{ system.users | dict2items }}"
   loop_control:
-    label: "{{ item.name | default('(unnamed)') }}"
+    label: "{{ item.key }}"
 
 - name: Validate system features input types
   when: system.features is defined