## What & why
First half of **S-12c** (behandel-portal backend), per **ADR-0013** (decisions recorded in #84):
- **BFF multi-realm auth.** A second JWT bearer scheme (`medewerker`) alongside the default `digid` scheme. On validation it lifts Keycloak's `realm_access.roles` onto the principal, and a `behandelaar` policy (medewerker scheme + `behandelaar` role) gates `/behandel/*`. Self-service keeps the digid scheme.
- **Werkbak = Flowable tasks.** The domain `Werkbak` query reads the open `Beoordelen` tasks (§8.2, S-12b's `IUserTaskClient`) and enriches each with its aggregate's bsn + status; `GET /behandel/werkbak` (domain) is proxied by the BFF `GET /behandel/werkbak` behind the behandelaar policy. The read projection stays the anonymous openbaar model (no premature `IN_BEHANDELING`/personal-data plumbing — deferred in ADR-0008).
Behavior: `/behandel/werkbak` is **401** without a token, **403** for a medewerker lacking the role, **200 + werkbak** for a behandelaar.
**S-12c-2** (next): `POST /behandel/registrations/{id}/decide` → domain decision + complete the Flowable task.
## Definition of Done
- [x] Linked issue: #13 (umbrella, `refs`); closes the adr-proposal #84
- [x] Tests first; red → green per layer
- [x] Unit + acceptance green (`make unit`): domain 78, bff 23, acceptance 9 (+ acl/event-subscriber unaffected)
- [x] api-client `test` green; openapi.json regenerated (drift guard passes)
- [x] Mutation ≥ break(90): **domain 100%, bff 100%**
- [x] ADR-0013 added; `Keycloak__MedewerkerAuthority` wired into compose
- [ ] CI green (pending)
Part of #13. closes#84
Reviewed-on: #85
Use-case-level BDD (Reqnroll) driving the real BFF over HTTP with fake downstreams
and locally-minted tokens: a valid DigiD token is accepted and the bsn forwarded
to the domain; a tokenless submit is 401; the openbaar register is anonymous and
never exposes the bsn (ADR-0010). Real Keycloak validation is the verify-bff check.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
