Mailman: add the admin UI to the notifications

Add a link to the admin UI to notifications sent about a held message.

See https://pagure.io/fedora-infrastructure/issue/6634

roles/mailman/files/mailman-template-list-admin-action-post.txt

@@ -0,0 +1,15 @@
+As list administrator, your authorization is requested for the
+following mailing list posting:
+
+    List:    $listname
+    From:    $sender_email
+    Subject: $subject
+
+The message is being held because:
+
+$reasons
+
+At your convenience, visit your dashboard to approve or deny the
+request:
+
+https://lists.fedoraproject.org/admin/lists/$list_id/held_messages

roles/mailman/tasks/main.yml

@@ -203,9 +203,17 @@
   - mailman
 
 - name: set default list footer
-  copy: src=mailman-generic-list-footer
-            dest=/var/lib/mailman3/templates/site/en/list:member:generic:footer.txt
-            owner=mailman group=mailman mode=0644
+  copy: src=mailman-template-list-member-generic-footer.txt
+        dest=/var/lib/mailman3/templates/site/en/list:member:generic:footer.txt
+        owner=mailman group=mailman mode=0644
+  tags:
+  - config
+  - mailman
+
+- name: set default list:admin:action:post template
+  copy: src=mailman-template-list-admin-action-post.txt
+        dest=/var/lib/mailman3/templates/site/en/list:admin:action:post.txt
+        owner=mailman group=mailman mode=0644
   tags:
   - config
   - mailman