feat(workflow): Flowable + registratie.bpmn external task (closes #4) (#44)

infra/flowable/docker-compose.yml

@@ -0,0 +1,65 @@
+# Flowable (S-03): the flowable-rest engine on Postgres.
+# The registratie.bpmn model is deployed via the REST API on startup by flowable-init.
+#
+#   docker compose -f infra/flowable/docker-compose.yml up -d
+#   # REST API (basic auth) under http://localhost:8090/flowable-rest/service/
+#
+# Host port 8090 (8000/8001/8080/8180 are taken by OpenZaak/NRC/BFF/Keycloak).
+services:
+  flowable-db:
+    image: docker.io/library/postgres:16
+    environment:
+      POSTGRES_USER: flowable
+      POSTGRES_PASSWORD: flowable
+      POSTGRES_DB: flowable
+    volumes:
+      - flowable-db:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U flowable -d flowable"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+    networks: [cg]
+
+  flowable-rest:
+    image: docker.io/flowable/flowable-rest:latest
+    environment:
+      SPRING_DATASOURCE_DRIVER-CLASS-NAME: org.postgresql.Driver
+      SPRING_DATASOURCE_URL: jdbc:postgresql://flowable-db:5432/flowable
+      SPRING_DATASOURCE_USERNAME: flowable
+      SPRING_DATASOURCE_PASSWORD: flowable
+    ports:
+      - "8090:8080"
+    depends_on:
+      flowable-db:
+        condition: service_healthy
+    networks: [cg]
+
+  # Deploys workflows/registratie.bpmn via the REST API once flowable-rest is up.
+  # Idempotent: skips if a deployment named "registratie" already exists.
+  flowable-init:
+    image: docker.io/curlimages/curl:latest
+    restart: "no"
+    volumes:
+      - ../../workflows/registratie.bpmn:/work/registratie.bpmn:ro,z
+    command:
+      - sh
+      - -c
+      - |
+        base=http://flowable-rest:8080/flowable-rest/service/repository/deployments
+        until curl -sf -u rest-admin:test "$$base" >/dev/null 2>&1; do echo "waiting for flowable-rest..."; sleep 3; done
+        if curl -s -u rest-admin:test "$$base?name=registratie" | grep -q '"name":"registratie"'; then
+          echo "registratie already deployed; skip"
+        else
+          curl -sf -u rest-admin:test -F 'file=@/work/registratie.bpmn;filename=registratie.bpmn' "$$base" >/dev/null && echo "deployed registratie"
+        fi
+    depends_on:
+      flowable-rest:
+        condition: service_started
+    networks: [cg]
+
+volumes:
+  flowable-db:
+
+networks:
+  cg: