ref: Install authorized keys per user

Instead of installing authorized keys globally (same for everybody), we
pass in the authorized_keys variable per user, and thus the installation
also takes place per user.

This makes much more sense and works with minimal refactoring.

roles/system/defaults/main.yaml

@@ -7,11 +7,10 @@ system_users:
       - marty
       - data
       - incus-admin
+    authorized_keys:
+      - "{{ lookup('file', '~/.ssh/keys/bob.pub') }}"
   - name: data
     groups:
       - data
     create_home: false
     shell: /sbin/nologin
-
-system_authorized_keys:
-  - "{{ lookup('file', '~/.ssh/keys/bob.pub') }}"