post
https://apis.kentro.live/store/v1/session.signup
Creates a buyer account on the store, by email or by phone, following the store's sign-up policy (store.get answers acquisition: the methods, the required fields, whether an invite code is needed, whether confirmation is required). Answers status: "confirmation-required" when a code was sent, or status: "complete" with whether the account is approved. Send the visitor's address as X-Storefront-Client-Ip so sign-up limits apply per visitor. The buyer then signs in at POST https://apis.kentro.live/auth/login/customer.
Who may call it: Anyone with the API key and the storefront host; no buyer or guest token is needed.
