gitlab: Send prometheus metrics to monitoring.al.org

roles/gitlab/defaults/main.yml

 gitlab_backupdir: /srv/gitlab/data/backups
+monitoring_domain: "{{ hostvars['monitoring.archlinux.org']['wireguard_address'] }}"

roles/gitlab/tasks/main.yml

@@ -97,6 +97,18 @@
         ]
         grafana['enable'] = false
         node_exporter['enable'] = false
+        prometheus['external_labels'] = {
+          'source' => 'gitlab'
+        }
+        prometheus['remote_write'] = [
+          {
+            url: 'http://{{ monitoring_domain }}:9090/api/v1/write',
+            basic_auth: {
+              username: '{{ vault_prometheus_monitoring_user }}',
+              password: '{{ vault_prometheus_monitoring_passwd }}'
+            }
+          }
+        ]
     volumes:
       - "/srv/gitlab/config:/etc/gitlab"
       - "/srv/gitlab/logs:/var/log/gitlab"