customerio-core-feature

# Customer.io Core Feature Integration

## Overview
Implement Customer.io core features: segments, transactional messaging, data pipelines, and broadcast campaigns.

## Prerequisites
- Customer.io SDK configured
- Understanding of customer data model
- App API credentials for transactional emails

## Instructions

### Feature 1: Transactional Messages
```typescript
// lib/customerio-transactional.ts
import { APIClient, RegionUS, SendEmailRequest } from '@customerio/track';

const apiClient = new APIClient(process.env.CUSTOMERIO_APP_API_KEY!, {
  region: RegionUS
});

interface TransactionalEmailOptions {
  to: string;
  transactionalMessageId: string;
  messageData?: Record<string, any>;
  identifiers?: { id?: string; email?: string };
}

export async function sendTransactionalEmail(options: TransactionalEmailOptions) {
  const request: SendEmailRequest = {
    to: options.to,
    transactional_message_id: options.transactionalMessageId,
    message_data: options.messageData,
    identifiers: options.identifiers
  };

  return apiClient.sendEmail(request);
}

// Usage examples
// Password reset
await sendTransactionalEmail({
  to: 'user@example.com',
  transactionalMessageId: 'password_reset',
  messageData: {
    reset_link: 'https://app.example.com/reset?token=abc123',
    expiry_hours: 24
  }
});

// Order confirmation
await sendTransactionalEmail({
  to: 'customer@example.com',
  transactionalMessageId: 'order_confirmation',
  messageData: {
    order_id: 'ORD-12345',
    items: [
      { name: 'Product A', quantity: 2, price: 29.99 }
    ],
    total: 59.98
  },
  identifiers: { id: 'user-456' }
});
```

### Feature 2: Segments
```typescript
// lib/customerio-segments.ts
import { TrackClient } from '@customerio/track';

// Update user attributes for segment membership
export async function updateUserForSegments(
  client: TrackClient,
  userId: string,
  attributes: {
    // Engagement metrics
    last_active_at?: number;
    session_count?: number;
    total_t