FEAT(loki): add journald scraping to promtail

vars/helm/005-loki.yml

@@ -3,3 +3,28 @@ loki:
   chart: grafana/loki-stack
   url: https://grafana.github.io/helm-charts
   namespace: metrics
+  vals:
+    promtail:
+      extraScrapeConfigs:
+        - job_name: journal
+          journal:
+            path: /var/log/journal
+            max_age: 12h
+            labels:
+              job: systemd-journal
+          relabel_configs:
+            - source_labels:
+                - '__journal__systemd_unit'
+              target_label: 'unit'
+            - source_labels:
+                - '__journal__hostname'
+              target_label: 'hostname'
+      extraVolumes:
+        - name: journal
+          hostPath:
+            path: /var/log/journal
+
+      extraVolumeMounts:
+        - name: journal
+          mountPath: /var/log/journal
+          readOnly: true