h-a: Add init container to wait for PostgreSQL

When Home Assistant starts, if PostgreSQL is unavailable, it will come
up successfully, but without the history component.  It never tries
again to connect and enable the component.  This makes it difficult to
detect the problem and thus easy to overlook the missing functionality.
To avoid having extended periods of missing state history, we'll force
Home Assistant to wait for PostgreSQL to come up before starting.

home-assistant/kustomization.yaml

@@ -47,6 +47,28 @@ patches:
     spec:
       template:
         spec:
+          initContainers:
+          - name: waitfordb
+            image: docker.io/library/postgres:15
+            command:
+            - sh
+            - -c
+            - until pg_isready; do sleep 1; done
+            env:
+            - name: PGHOST
+              value: default.postgresql
+            - name: PGGDATABASE
+              value: homeassistant
+            - name: PGUSER
+              valueFrom:
+                secretKeyRef:
+                  name: home-assistant.homeassistant.default.credentials.postgresql.acid.zalan.do
+                  key: username
+            - name: PGPASSWORD
+              valueFrom:
+                secretKeyRef:
+                  name: home-assistant.homeassistant.default.credentials.postgresql.acid.zalan.do
+                  key: password
           containers:
           - name: home-assistant
             env: