fix(monitoring): provide alertmanager minimal config

monitoring/alertmanager/config.yml

@@ -0,0 +1,12 @@
+global:
+  resolve_timeout: 5m
+route:
+  receiver: "null"
+  group_by:
+    - job
+  group_wait: 30s
+  group_interval: 5m
+  repeat_interval: 12h
+receivers:
+  - name: "null"
+