intercom: HMAC / JWT (auth_tokens) identity verification as typed required field

[productdevbook]

Intercom's Identity Verification (HMAC of `user_id` with the app secret) plus the newer `intercom_user_jwt` flow keeps getting added as prop strings with no type enforcement — so devs forget and bots leak data.

Evidence

• `Add support for auth_tokens in boot and update methods devrnt/react-use-intercom#820` — "Add support for `auth_tokens` in boot/update" Add support for auth_tokens in boot and update methods devrnt/react-use-intercom#820
• `Support for intercom_user_jwt prop devrnt/react-use-intercom#813` — "Support for `intercom_user_jwt`" (workaround: shove JWT into customAttributes) Support for intercom_user_jwt prop devrnt/react-use-intercom#813
• `User Hash Property / Formatting devrnt/react-use-intercom#668` — "User Hash Property / Formatting" User Hash Property / Formatting devrnt/react-use-intercom#668
• `Support for user_hash for Identify Verification nhagen/react-intercom#61` — "Support for `user_hash`" Support for user_hash for Identify Verification nhagen/react-intercom#61

Tasks

• `load({ appId, verification: "hmac" | "jwt" | "none" })`
• When `verification !== "none"`, `identify()` requires `{ hash }` or `{ token }` at type level
• Docs page with Node / Python / Ruby / Go snippets for server-side HMAC
• Warn in dev if `identify()` called with email but no hash and app enforces verification

[productdevbook]

Implemented in this commit