Declare the classic-models topics and a credentials store

Topics are declared rather than auto-created: the application account has no
Create ACL, so a producer would have been denied, and an auto-created topic
takes broker defaults nobody chose.

The credentials store lets an application namespace read its own KafkaUser
password and the cluster CA from the kafka namespace, so the password stays
generated and rotatable by Strimzi instead of being copied by hand.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

kafka-topics.yaml

@@ -0,0 +1,56 @@
+---
+# Topics are declared, never auto-created.
+#
+# Two reasons. An application account has no Create ACL — a producer that can
+# invent topics can also invent a typo and publish into it for weeks with nobody
+# noticing. And auto-created topics take the broker defaults, which is how a
+# topic that should be compacted and retained for a year ends up deleted after
+# seven days.
+#
+# One topic per aggregate. Partition count is the ceiling on consumer
+# parallelism and cannot be lowered later, so it is set for the traffic
+# expected, not for the traffic today.
+apiVersion: kafka.strimzi.io/v1
+kind: KafkaTopic
+metadata:
+  name: classic-models.catalog
+  namespace: kafka
+  labels:
+    strimzi.io/cluster: kafka
+spec:
+  partitions: 3
+  replicas: 1
+  config:
+    retention.ms: "604800000"   # 7 days
+    cleanup.policy: delete
+    min.insync.replicas: "1"
+---
+apiVersion: kafka.strimzi.io/v1
+kind: KafkaTopic
+metadata:
+  name: classic-models.sales
+  namespace: kafka
+  labels:
+    strimzi.io/cluster: kafka
+spec:
+  partitions: 3
+  replicas: 1
+  config:
+    retention.ms: "604800000"
+    cleanup.policy: delete
+    min.insync.replicas: "1"
+---
+apiVersion: kafka.strimzi.io/v1
+kind: KafkaTopic
+metadata:
+  name: classic-models.payments
+  namespace: kafka
+  labels:
+    strimzi.io/cluster: kafka
+spec:
+  partitions: 3
+  replicas: 1
+  config:
+    retention.ms: "604800000"
+    cleanup.policy: delete
+    min.insync.replicas: "1"