borgmatic is run under user root so postgres superuser doesn't match peer

roles/borgmatic/templates/borgmatic.d/config.yml.j2

@@ -69,7 +69,7 @@ hooks:
     postgresql_databases:
 {% for hook in borgmatic_hooks.postgresql_databases %}
         - name: {{ hook.name | default('all') }}
-          username: {{ hook.username | default('postgres') }}
+          username: {{ hook.username | default('root') }}
           format: {{ hook.format | default('custom') }}
 {% endfor %}
 {% endif %}

roles/mailserver_database/tasks/main.yml

@@ -9,6 +9,14 @@
       - python3-psycopg2
       - acl
 
+- name: Create root postgresql superuser, needed for backups
+  become: true
+  become_user: postgres
+  community.postgresql.postgresql_user:
+    name: root
+    state: present
+    role_attr_flags: SUPERUSER
+
 - name: Create postgresql users
   become: true
   become_user: postgres