v-m/alertmanager: Migrate PVC to Synology

We also don't need a 4 GB volume for AlertManager; even 500 MB is
way too big for the tiny amount of data it stores, but that's about the
smallest size a filesystem can be.

victoria-metrics/alertmanager.yaml

@@ -83,4 +83,4 @@ spec:
       - ReadWriteOnce
       resources:
         requests:
-          storage: 4G
+          storage: 500M

victoria-metrics/kustomization.yaml

@@ -216,6 +216,16 @@ patches:
             - --cluster.peer=alertmanager-0.alertmanager:9094
             - --cluster.peer=alertmanager-1.alertmanager:9094
 
+- patch: |
+    - op: add
+      path: /spec/volumeClaimTemplates/0/spec/storageClassName
+      value: synology-iscsi
+  target:
+    group: apps
+    version: v1
+    kind: StatefulSet
+    name: alertmanager
+
 - patch: |
     - op: add
       path: /spec/volumeClaimTemplates/0/spec/storageClassName