The withdraw handler returns an outcome and refuses a bsn that doesn't own the registration; the
BFF endpoint requires a digid token, forwards id+bsn, and relays the domain's 404.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
## What & why
Second sub-slice of **S-11 · Withdrawal (Flow 3)** (#12). S-11a (#88) made a withdrawal advance the aggregate to INGETROKKEN; this sub-slice **cancels the running Flowable process** so the withdrawn case leaves the behandelaar's werkbak.
- **BPMN** (`registratie.bpmn`): an interrupting message boundary event (`RegistratieIngetrokken`) on the `Beoordelen` task, routing to a dedicated "Registratie ingetrokken" end event.
- **Workflow Client**: `WithdrawBeoordelingAsync(executionId)` delivers `messageEventReceived` to the task's execution (PUT); `BeoordelingTask` now carries its `executionId`.
- **`WithdrawRegistration` handler**: after the domain transition, finds the open `Beoordelen` task for the registration and delivers the withdrawal message — best-effort, mirroring how the beoordeling completes its task.
- **Werkbak**: also filters out registrations that are no longer open, so a withdrawn case never surfaces even in the brief window before cancellation lands.
- **ADR-0014** records the decision (message event in BPMN vs. deleting the instance from code).
- **verify (`run-domain-check.sh`)**: a second registration parks at `Beoordelen`, is withdrawn via the domain, and the check asserts its `Beoordelen` task disappears — so verify-stack validates the live Flowable message correlation.
Refs #12 (S-11c — the BFF + self-service "trek aanvraag in" button + e2e — closes it).
## Definition of Done
- [x] Linked Gitea issue (#12).
- [x] Failing tests committed before the implementation (red → green per commit).
- [x] Implementation makes the tests pass.
- [x] Conventional Commits referencing the issue (`refs #12`).
- [ ] CI green — all Gitea Actions jobs.
- [x] `docker compose up` unaffected (BPMN redeploys on a fresh CI DB via flowable-init).
- [x] ADR added (ADR-0014).
- [x] Docs — the user-visible demo note lands with S-11c.
## Notes for reviewers
- Verified locally: `Big.Tests` 94/94 pass; `Big.Api` builds; `registratie.bpmn` is well-formed.
- The Flowable message-correlation REST shape is validated **live** by verify-stack (the Workflow Client unit tests stub the exchange and assert only the request shape, per ADR-0009) — the new `run-domain-check.sh` withdrawal step is that live check.
- Known gap (ADR-0014): a withdrawal that races ahead of the process reaching `Beoordelen` finds no task to cancel; the aggregate is still INGETROKKEN and the werkbak filter hides it, but that instance parks unattended. A process-level event subprocess would close the gap — deferred.
Reviewed-on: #89
## What & why
First sub-slice of **S-11 · Withdrawal (Flow 3)** (#12). A zorgprofessional can withdraw a still-open registration ("trek aanvraag in"); this sub-slice delivers the **domain transition + endpoint**, mirroring how S-12a shipped the beoordeling decision model on its own (#82).
- `RegistrationStatus.Ingetrokken` (terminal).
- `Registration.Withdraw()` — allowed from INGEDIEND or IN_BEHANDELING, needs no zaak, idempotent, and rejected once the registration has been decided (INGESCHREVEN/AFGEWEZEN).
- `WithdrawRegistration` application handler (load → withdraw → persist; repeated withdrawal is a no-op).
- `POST /registrations/{id}/withdraw` on the domain API.
Demoable: `POST /registrations/{id}/withdraw` → `GET /registrations/{id}` shows `INGETROKKEN`.
Refs #12 (not closing — see below).
## Scope / follow-ups
S-11 is bigger than one slice, so it is split (CLAUDE.md §13), like S-12 was:
- **S-11a (this PR)** — domain withdrawal transition + endpoint.
- **S-11b** — cancel the running Flowable process via a BPMN message event, so a withdrawn case leaves the behandelaar's werkbak.
- **S-11c** — owner-scoped BFF self-service withdraw endpoint + "trek aanvraag in" button + e2e.
Cancelling the Flowable process is deliberately deferred (documented in `WithdrawRegistration`), exactly as the beoordeling's rejection deferred its zaak propagation. #12 stays open until S-11c.
## Definition of Done
- [x] Linked Gitea issue (#12).
- [x] Failing test committed before the implementation.
- [x] Implementation makes the test pass.
- [x] Conventional Commits referencing the issue (`refs #12`).
- [ ] CI green — all Gitea Actions jobs.
- [x] `docker compose up` unaffected (no infra/contract change).
- [x] Docs — none needed for this backend sub-slice; the user-visible demo note lands with S-11c.
- [x] No ADR needed — mirrors existing aggregate/handler/endpoint patterns; no boundary change.
## Notes for reviewers
- Verified locally: `Big.Tests` 89/89 pass; `Big.Api` builds clean.
- The domain trusts its callers (§8.3); owner-scoping by the caller's bsn is enforced at the BFF in S-11c.
Reviewed-on: #88
