✉️ Email Notification Adapter

This PR introduces a provider-agnostic email notification system with support for pluggable providers, templated emails, and a mock provider for development and testing.

🎯 Purpose

Improve notification reliability and flexibility by decoupling email delivery from specific providers while enabling reusable, event-based email templates.

✅ What’s Included

🔌 Provider-Agnostic Email Adapter

• Introduced a common EmailAdapter interface
• Enables seamless swapping between providers (SendGrid, SES, Mailgun, etc.)
• Adapter selection is environment-driven

🧪 Mock Email Provider

• Safe mock provider for local development and CI
• Prevents real email delivery outside production
• Logs send attempts for visibility

📨 Templated Emails

• Handlebars-based email templates
• Templates created for:
  • Booking events (confirmation, cancellation)
  • Payment events (success, failure)
• Clean separation between template structure and dynamic data

⚙️ Configuration

• Provider selection via environment variables
• Supports future providers with zero changes to consumers

📊 Logging

• Centralized email logging (email.logger.ts)
• Logs send attempts, successes, and failures
• Ready for integration with centralized logging/tracing systems

🧪 Tests

• Unit tests for:
  • Adapter behavior
  • Template rendering
  • Email service execution flow

🧩 Example Usage

await notify.sendEmail({
  to: user.email,
  subject: 'Booking Confirmed',
  template: 'booking/booking-confirmed',
  data: {
    userName: user.name,
    serviceName: booking.service,
    date: booking.date,
    reference: booking.ref,
  },
});

CLoses #149