Updates for grafana stack

roles/observability/templates/grafana-datasources.yml.j2

@@ -0,0 +1,21 @@
+# Managed by Ansible (roles/observability). Do not edit by hand.
+apiVersion: 1
+
+datasources:
+  - name: Loki
+    type: loki
+    access: proxy
+    url: http://loki:3100
+    isDefault: false
+    editable: false
+    jsonData:
+      maxLines: 1000
+
+  - name: Prometheus
+    type: prometheus
+    access: proxy
+    url: http://prometheus:9090
+    isDefault: true
+    editable: false
+    jsonData:
+      timeInterval: 15s