Add db backups to gitea

This isn't added as a separate role because it heavily relies on the
gitea deployment specific (docker-compose, service names, etc). If we
end up running more services with docker-compose and databases we can
probably make this reconsumable.

Change-Id: I7b9084a8a90a86f73f5b24de505978d3f286850b

playbooks/roles/gitea/tasks/main.yaml

@@ -134,3 +134,26 @@
     minute: 37
     hour: 12
     weekday: 0
+- name: Create db backup dest
+  file:
+    state: directory
+    path: /var/backups/gitea-mariadb
+    mode: 0700
+    owner: root
+    group: root
+- name: Set up cron job to backup the database
+  cron:
+    name: gitea-db-backup
+    state: present
+    user: root
+    job: >
+      /usr/bin/docker-compose -f /etc/gitea-docker/docker-compose.yaml exec -T mariadb
+      bash -c '/usr/bin/mysqldump --opt --ignore-table mysql.event --all-databases --single-transaction -uroot -p"$MYSQL_ROOT_PASSWORD"' |
+      gzip -9 > /var/backups/gitea-mariadb/gitea-mariadb.sql.gz
+    minute: 42
+    hour: 4
+- name: Rotate db backups
+  include_role:
+    name: logrotate
+  vars:
+    logrotate_file_name: /var/backups/gitea-mariadb/gitea-mariadb.sql.gz