Restart the router when its routing config changes (2.0.0+up1.46.4)

The deployment now carries a checksum/config annotation over the rendered
ConfigMap, so a changed routing table produces a new pod template and a
controlled rollout.

Without it a mapping change was inert but looked successful: the file is
mounted with subPath (kubelet never refreshes those in a running container)
and mc-router reads ROUTES_CONFIG only at startup. That combination caused the
minecraft-server stage-3 outage - the ConfigMap pointed at the renamed
services, the running router kept proxying to the old ones, and the pod stayed
Ready throughout.

Major bump: runtime behaviour changes. A mapping change now costs a router
restart (~4.5 s in k3d, so roughly 17-19 s in the real cluster) during which
clients cannot connect. That restart is what makes the change take effect at
all.

Refs #82.

minecraft-router/templates/minecraft-router.deployment.yaml

@@ -14,6 +14,13 @@ spec:
       name: {{ .Release.Name }}-{{ .Chart.Name }}-deployment
       labels:
         app: {{ .Release.Name }}-{{ .Chart.Name }}-deployment
+      annotations:
+        # Rolls the pod whenever the rendered routing ConfigMap changes.
+        # Without it a changed routing table stays inert: the file is mounted
+        # with subPath (kubelet never refreshes those in a running container)
+        # and mc-router reads ROUTES_CONFIG only at startup, so the router
+        # would keep serving the old routes while everything looks healthy.
+        checksum/config: {{ include (print $.Template.BasePath "/minecraft-router.configmap.yaml") . | sha256sum }}
     spec:
       automountServiceAccountToken: false
       securityContext: