customerio-upgrade-migration

# Customer.io Upgrade & Migration ## Current State !`npm list customerio-node 2>/dev/null | grep customerio || echo 'customerio-node: not installed'` !`npm view customerio-node version 2>/dev/null || echo 'Cannot check latest version'` ## Overview Plan and execute `customerio-node` SDK upgrades safely: assess current version, review breaking changes, apply code migrations, and validate with staged rollout. ## Prerequisites - Current SDK version identified (`npm list customerio-node`) - Test environment available - Version control for rollback ## Major Version Migration Reference ### Legacy `CustomerIO` to Modern `TrackClient` + `APIClient` Older versions of `customerio-node` used a single `CustomerIO` class. Modern versions split into `TrackClient` (tracking) and `APIClient` (transactional/broadcasts). ```typescript // BEFORE — Legacy pattern (customerio-node < 2.x) const CustomerIO = require("customerio-node"); const cio = new CustomerIO(siteId, apiKey); cio.identify("user-1", { email: "user@example.com" }); cio.track("user-1", { name: "event_name" }); // AFTER — Modern pattern (customerio-node >= 2.x) import { TrackClient, APIClient, RegionUS } from "customerio-node"; const cio = new TrackClient(siteId, apiKey, { region: RegionUS }); await cio.identify("user-1", { email: "user@example.com" }); await cio.track("user-1", { name: "event_name", data: {} }); const api = new APIClient(appApiKey, { region: RegionUS }); await api.sendEmail(request); ``` **Key changes:*...