Move matrix-bot-draupnir to its own container network

roles/custom/matrix-bot-draupnir/tasks/validate_config.yml

@@ -1,9 +1,10 @@
 ---
 
-- name: Fail if required variables are undefined
+- name: Fail if required matrix-bot-draupnir variables are undefined
   ansible.builtin.fail:
     msg: "The `{{ item }}` variable must be defined and have a non-null value."
   with_items:
     - "matrix_bot_draupnir_access_token"
     - "matrix_bot_draupnir_management_room"
+    - "matrix_bot_draupnir_container_network"
   when: "vars[item] == '' or vars[item] is none"