feat: update kanidm replicaiton (#169)

- split to per-server configs
- remove init containers that attempted to automate the replication config
- add README.md

Reviewed-on: #169

apps/base/kanidm/README.md

@@ -0,0 +1,32 @@
+# kanidm
+
+Single-replica kanidm identity server deployment.
+
+## Initial setup
+
+After the pod starts for the first time, generate the admin and idm_admin credentials:
+
+```bash
+kubectl exec -n kanidm kanidm-0 -- /sbin/kanidmd recover-account admin
+kubectl exec -n kanidm kanidm-0 -- /sbin/kanidmd recover-account idm_admin
+```
+
+## Adding replication
+
+If replication is needed in the future:
+
+1. Scale the StatefulSet to 3 replicas and add `podAntiAffinity` to spread across nodes.
+2. Add a `[replication]` section to `configmap.yaml` per pod (origin is pod-specific:
+   `repl://kanidm-N.kanidm-headless.kanidm.svc.cluster.local:8444`).
+3. Add the replication port (8444) back to the StatefulSet container ports and headless service.
+4. Restore `rbac.yaml` for the cert-publisher sidecar, or exchange certificates manually:
+
+```bash
+# On each pod, get its replication certificate
+kubectl exec -n kanidm kanidm-0 -- /sbin/kanidmd renew-replication-certificate
+
+# Add each peer's certificate to the other pods' configs under:
+# [replication."repl://<peer-fqdn>:8444"]
+# type = "mutual-pull"
+# partner_cert = "<cert>"
+```