Request a Meta re-verification code for a BYO WhatsApp number

For a bring-your-own WhatsApp number (its own WABA, migrated off another BSP) that Meta demoted to re-verification, this requests a new OTP from Meta. The code lands on the customer's own handset, so verifying it is necessarily self-service; call POST /v1/accounts/{accountId}/whatsapp/verify-code with the code once it arrives. Rate-limited to one request per 10 minutes per account, and Meta enforces its own cooldown on top of that.