Set mailman3 site-owner

This was missed in the original Ansibling because unlike all the other
settings it does not use an env var to set it. Instead we have to write
a file that the container startup scripts will append to the actual
config.

The comment for this value says it should be a human so we set it to the
root address of the running host which should end up in infra rooter
inboxes.

Change-Id: I235dfcba53c029136c141382920279ab593d1f82

playbooks/roles/mailman3/tasks/main.yaml

@@ -35,6 +35,15 @@
     group: 65533
     mode: '0755'
 
+- name: Copy our mailman-extra.cfg for mailman-core
+  template:
+    src: mailman-extra.cfg.j2
+    dest: /var/lib/mailman/core/mailman-extra.cfg
+    # TODO: undo for https://github.com/maxking/docker-mailman/issues/550
+    owner: 100
+    group: 65533
+    mode: '0644'
+
 - name: Ensure Mailman database volume directory exists
   file:
     state: directory

playbooks/roles/mailman3/templates/mailman-extra.cfg.j2

@@ -0,0 +1,6 @@
+[mailman]
+# This address is the "site owner" address.  Certain messages which must be
+# delivered to a human, but which can't be delivered to a list owner (e.g. a
+# bounce from a list owner), will be sent to this address.  It should point to
+# a human.
+site_owner: "root@{{ ansible_fqdn }}"