Onboarding Flow

---

Complete end-to-end flow to onboard a new end customer and send their first invoice.

Step-by-step flow

1. POST /auth/login                                    (partnerApiKey)   → partner JWT
2. POST /white-label-partner/create-user               (partner JWT)     → userId
3. POST /white-label-partner/create-company            (partner JWT)     → companyId + companyApiKey
4. POST /white-label-partner/register-request          (partner JWT)     → status
5. POST /invoice/send-document-async-json              (company JWT)     → trackingId
6. GET  /invoice/document-status/{trackingId}          (company JWT)     → COMPLETED