Embedded Signup Launcher
Use this onboarding page to launch either standard Business API onboarding or coexistence onboarding (existing WhatsApp Business App number) without exposing internal secrets in the browser.
Coexistence launch uses Meta-recommended parameters:
featureType=whatsapp_business_app_onboarding and
sessionInfoVersion=3.
Waiting for input. Create signed state first, then launch the desired onboarding mode.