inventory, roles, config, docs: update all files to refactor the ansible variables structure

config/services/systemd/fw/ddns/ddns.service.j2

@@ -12,4 +12,4 @@ StandardError=journal
 EnvironmentFile=/etc/secrets/%U/ddns.env
 
 # Run the script
-ExecStart=/usr/local/bin/ddns.sh -d "ilnmors.com"
+ExecStart=/usr/local/bin/ddns.sh -d "{{ domain['public'] }}"

config/services/systemd/fw/kea/kea-dhcp4.conf.j2

@@ -19,7 +19,7 @@
                     },
                     {
                         "name": "domain-name",
-                        "data": "ilnmors.internal."
+                        "data": "{{ domain['internal'] }}."
                     }
                 ],
                 "reservations": [
@@ -65,7 +65,7 @@
                     },
                     {
                         "name": "domain-name",
-                        "data": "ilnmors.internal."
+                        "data": "{{ domain['internal'] }}."
                     }
                 ],
                 "id": 2,