feat(bind9): support systemd drop-ins

Keep role configuration namespaced and allow hosts to customize systemd startup.

Co-authored-by: Copilot <copilot@github.com>

tasks/create_dnssec_files.yaml

@@ -4,8 +4,8 @@
   ansible.builtin.copy:
     dest: "{{ item.private.filename }}"
     content: "{{ item.private.content }}"
-    owner: "{{ bind_unix_user }}"
-    group: "{{ bind_unix_group }}"
+    owner: "{{ bind9_unix_user }}"
+    group: "{{ bind9_unix_group }}"
     mode: "0600"
   no_log: true
   with_items:
@@ -16,8 +16,8 @@
   ansible.builtin.copy:
     dest: "{{ item.public.filename }}"
     content: "{{ item.public.content }}"
-    owner: "{{ bind_unix_user }}"
-    group: "{{ bind_unix_group }}"
+    owner: "{{ bind9_unix_user }}"
+    group: "{{ bind9_unix_group }}"
     mode: "0644"
   no_log: true
   with_items: