FORMAT: use jsonnet for templating

* add jsonnet templates
* rewrite all charts to jsonnet

k8s-manifests/monitoring/loki-stack.jsonnet

@@ -0,0 +1,37 @@
+# vim:expandtab:
+local helmapp = import "../../_templates/argo_helm_app.template";
+
+[
+helmapp + {
+  name:: "loki",
+  namespace:: "metrics",
+  repo:: "https://grafana.github.io/helm-charts",
+  chart:: "loki-stack",
+  version:: "2.6.1",
+  values:: |||
+    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
+  |||
+}
+]