Add validation task for potential conflict between mautrix-instagram and mautrix-meta-instagram

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3138 and 367af472ea

roles/custom/matrix-base/tasks/validate_config.yml

@@ -85,3 +85,15 @@
       To clean up your server from mx-puppet-skype's presence, see this changelog entry: https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/master/CHANGELOG.md#mx-puppet-skype-removal.
       If you still need bridging to Skype, consider switching to the go-skype bridge instead. See `docs/configuring-playbook-bridge-go-skype-bridge.md`.
   when: "'matrix_mx_puppet_skype_enabled' in vars"
+
+- name: Fail if mautrix-instagram and mautrix-meta-instagram are in conflict
+  ansible.builtin.fail:
+    msg: >-
+      Your configuration enables both the old mautrix-instagram bridge and the new mautrix-meta-instagram bridge.
+      By default, both bridges are configured to use the same bridge bot username (`@{{ matrix_mautrix_meta_instagram_appservice_username }}:{{ matrix_domain }}`) which is a conflict.
+      We recommend that you disable at least one of the bridges (preferrably the old mautrix-instagram bridge), or to resolve the conflict in another way.
+      To resolve the conflict without disabling a bridge, consider adjusting one of `matrix_mautrix_instagram_appservice_bot_username` or `matrix_mautrix_meta_instagram_appservice_username` - they both have a value of {{ matrix_mautrix_meta_instagram_appservice_username }} right now.
+  when:
+    - matrix_mautrix_instagram_enabled | bool
+    - matrix_mautrix_meta_instagram_enabled | bool
+    - matrix_mautrix_instagram_appservice_bot_username == matrix_mautrix_meta_instagram_appservice_username