Add a dummy canary so we can detect if alerts are being loaded

Author: hectorhuertas

common/canary.yaml

@@ -0,0 +1,10 @@
+# PROMETHEUS RULES
+# DO NOT REMOVE line above, used in `pre-commit` hook
+
+groups:
+  # Allows detecting if alerts are being loaded in thanos-rule
+  - name: canary
+    rules:
+      # The alert is dummy, will never trigger
+      - alert: NoOpCanary
+        expr: vector(0)

common/kustomization.yaml

@@ -5,6 +5,7 @@ configMapGenerator:
   - files:
       - all.yaml.tmpl=all.yaml.tmpl
       - logging.yaml.tmpl=logging.yaml.tmpl
+      - canary.yaml.tmpl
       - container.yaml.tmpl
       - missing_replicas.yaml.tmpl
       - namespace_sync.yaml.tmpl