S-18c · RegisterRecord objecttype defined + registered (closes #141) (#146)

## What & why

S-18c, the **final** slice of the S-18 (#19) split (after S-18a #142, S-18b #143). Defines the **RegisterRecord** objecttype — the schema S-19 (#20) will write canonical register records against on approval — and registers it in the Objecttypen API at startup.

Closes #141

### What

- **Schema** (`infra/objecttypen-registerrecord/registerrecord.schema.json`): public-safe by construction — `id`, `status` (enum `INGEDIEND`/`INGESCHREVEN`), `reference` only, `additionalProperties: false`, `dataClassification: open`. Mirrors the BFF's `OpenbaarEntry` — **no `bsn`/`naam`** (ADR-0027).
- **Registration**: a `registerrecord-init` compose one-shot (stdlib Python on the stack network) POSTs the objecttype + a **published** version over the API once Objecttypen is healthy. The Objecttypen `setup_configuration` (3.4.2) only provisions tokens — no declarative objecttype step — so this follows the ADR-0020 self-seed pattern. **Idempotent**: if a `RegisterRecord` with a version already exists it is a no-op.
- **Wiring**: schema + `register.py` streamed into the external `rr-registerrecord-config` volume by `seed-config.sh registerrecord` (main) / bind-mounted (local); added to `SEED`, `CFG_VOLS`, and the CI log-dump. `registerrecord-init` is a one-shot (not in `WAIT_SVCS`).
- **Smoke**: `verify-registerrecord` (`run-registerrecord-check.sh` + `registerrecord-check.py`) asserts the objecttype exists, has a **published** version, and that version's schema carries `id`/`status`/`reference`; added as a verify-stack step + a row in the #136 summary.
- **ADR-0027**: records the public-safe schema decision (mirror the BFF public view, not the internal projection; API-seeded one-shot). The slice issue #141 flagged the schema as ADR-worthy, so no separate adr-proposal issue was opened.

## Verified locally (end to end, real compose)

Seeded `rr-registerrecord-config`, brought Objecttypen up, ran `registerrecord-init` → `registered RegisterRecord <uuid> v1 (published)`. `make verify-registerrecord` → **OK — RegisterRecord v1 published, fields=['id', 'reference', 'status']**. Re-running the one-shot → **no-op** (idempotent). `docker compose config` clean on both files; schema + script + ci.yaml validated.

## Definition of Done

- [x] Failing smoke committed first (`test(infra): …`, "no objecttype named RegisterRecord"); implementation makes it pass.
- [x] Conventional Commits referencing #141.
- [x] CI green (verify-stack registerrecord step — validated locally; runner already unstarved by #145).
- [x] `docker compose up` reaches health (one-shot registers after Objecttypen healthy).
- [x] Docs: ADR-0027 + demo note.
- [x] Closed by the merging PR (`closes #141`).

This closes out the S-18 (#19) split — Objecttypen (S-18a) + Objecten (S-18b) + RegisterRecord (S-18c) are all up. Next: **S-19 (#20)** — ACL writes the register record to Objecten on approval, against this schema.

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #146

docs/demo-script.md

@@ -5,6 +5,35 @@ copy-pasteable walkthrough against a local `make up` stack.
 
 ---
 
+## S-18c — RegisterRecord objecttype defined + registered (#141, ADR-0027)
+
+**Outcome:** a **RegisterRecord** objecttype with a **published** JSON schema is registered in the
+Objecttypen API at startup. The schema is public-safe by construction — `id`, `status`, `reference`
+only, mirroring the BFF's `OpenbaarEntry` (no `bsn`/`naam`), `dataClassification: open`. This is the
+schema S-19 writes register records against on approval. A `registerrecord-init` one-shot creates it
+over the API once Objecttypen is healthy (the Objecttypen `setup_configuration` has no objecttype
+step), idempotently.
+
+```bash
+make up
+# The RegisterRecord objecttype exists with a published version:
+curl -s -H "Authorization: Token 0123456789abcdef0123456789abcdef01234567" \
+  "http://localhost:8020/api/v2/objecttypes" | python3 -c \
+  'import sys,json; o=[x for x in json.load(sys.stdin)["results"] if x["name"]=="RegisterRecord"][0]; print(o["name"], o["dataClassification"], o["versions"])'
+#   → RegisterRecord open ['http://.../objecttypes/<uuid>/versions/1']
+#
+# Automated (a CI verify-stack step): asserts the objecttype exists, has a published version, and
+# that version's schema carries id/status/reference.
+make verify-registerrecord     # → OK — RegisterRecord v1 published, fields=['id', 'reference', 'status']
+```
+
+**The path:** `infra/objecttypen-registerrecord/registerrecord.schema.json` (the reviewed public-safe
+contract) + `register.py` are streamed into an external config volume by `infra/seed-config.sh
+registerrecord` (bind-mounted locally); the `registerrecord-init` one-shot POSTs the objecttype + a
+published version. Re-running is a no-op. S-19 (#20) writes records against this schema in Objecten.
+
+---
+
 ## S-18b — Objecten API up in compose, wired to Objecttypen (#140)
 
 **Outcome:** the upstream Maykin **Objecten API** runs in the stack — own **PostGIS** DB + redis,