Split bind-external DNSRecords into one file per record (#500)

A single records.yaml holding every DNSRecord means any record change touches a shared file, and deleting one record is a hunk edit rather than a file removal. One file per record under <zone>/<type>/<record>.yaml makes each record independently editable and removable.

- move acme-apex-ns to acme-unkin-net/ns/apex.yaml and acme-ns1-a to acme-unkin-net/a/ns1.yaml
- add kustomization.yaml per zone and type directory, referencing directories from the parent
- carry the delegation rationale onto the zone kustomization
- drop records.yaml and reference the zone directory from the app kustomization

Rendered output is unchanged.

Reviewed-on: #500
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

apps/base/bind-external/acme-unkin-net/a/kustomization.yaml

@@ -0,0 +1,6 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - ns1.yaml

apps/base/bind-external/acme-unkin-net/a/ns1.yaml

@@ -0,0 +1,16 @@
+---
+apiVersion: bind.unkin.net/v1alpha1
+kind: DNSRecord
+metadata:
+  name: acme-ns1-a
+  namespace: bind-external
+spec:
+  zoneRef: acme-unkin-net
+  name: ns1
+  type: A
+  ttl: 3600
+  values:
+    # Public address of this cluster's external BIND, same target as
+    # acme-ns1.unkin.net. Resolvers that cached the seeded ns1.acme.unkin.net
+    # NS name must still reach the zone.
+    - 103.216.191.185

apps/base/bind-external/acme-unkin-net/kustomization.yaml

@@ -0,0 +1,11 @@
+---
+# Authoritative delegation records for acme.unkin.net. Without these the zone
+# only holds the operator's seed apex (NS ns1.acme.unkin.net glued to the
+# primary pod IP), which is unroutable off-cluster and goes stale on
+# reschedule. DNSRecords must live in the same namespace as their BindZone.
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - ns
+  - a

apps/base/bind-external/acme-unkin-net/ns/apex.yaml

@@ -0,0 +1,16 @@
+---
+apiVersion: bind.unkin.net/v1alpha1
+kind: DNSRecord
+metadata:
+  name: acme-apex-ns
+  namespace: bind-external
+spec:
+  zoneRef: acme-unkin-net
+  # "@" is the zone apex.
+  name: "@"
+  type: NS
+  ttl: 3600
+  values:
+    # Matches the parent delegation in Google Cloud DNS. Out of zone, so the
+    # child needs no glue of its own.
+    - acme-ns1.unkin.net.

apps/base/bind-external/acme-unkin-net/ns/kustomization.yaml

@@ -0,0 +1,6 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - apex.yaml

apps/base/bind-external/kustomization.yaml

@@ -7,5 +7,5 @@ resources:
   - cluster.yaml
   - tsigkey.yaml
   - zones.yaml
-  - records.yaml
+  - acme-unkin-net
   - agent-dns-rolebinding.yaml

apps/base/bind-external/records.yaml

@@ -1,36 +0,0 @@
-# Authoritative delegation records for acme.unkin.net. Without these the zone
-# only holds the operator's seed apex (NS ns1.acme.unkin.net glued to the
-# primary pod IP), which is unroutable off-cluster and goes stale on
-# reschedule. DNSRecords must live in the same namespace as their BindZone.
----
-apiVersion: bind.unkin.net/v1alpha1
-kind: DNSRecord
-metadata:
-  name: acme-apex-ns
-  namespace: bind-external
-spec:
-  zoneRef: acme-unkin-net
-  # "@" is the zone apex.
-  name: "@"
-  type: NS
-  ttl: 3600
-  values:
-    # Matches the parent delegation in Google Cloud DNS. Out of zone, so the
-    # child needs no glue of its own.
-    - acme-ns1.unkin.net.
----
-apiVersion: bind.unkin.net/v1alpha1
-kind: DNSRecord
-metadata:
-  name: acme-ns1-a
-  namespace: bind-external
-spec:
-  zoneRef: acme-unkin-net
-  name: ns1
-  type: A
-  ttl: 3600
-  values:
-    # Public address of this cluster's external BIND, same target as
-    # acme-ns1.unkin.net. Resolvers that cached the seeded ns1.acme.unkin.net
-    # NS name must still reach the zone.
-    - 103.216.191.185