Dayuse Mail — DTO Pattern

Overview

Modernization pattern for Dayuse transactional emails: replace unstructured arrays (reservationData, array<string, mixed>) with strictly typed PHP DTOs (final readonly class) with a static build() method, and .dto.html.twig templates with zero business logic.

When to Use This Skill

• Refactoring legacy transactional email templates (.html.twig).
• Migrating templates to the .dto.html.twig extension.
• Replacing the global unstructured array reservationData (and other array<string, mixed> arrays) with specific DTOs with typed properties.
• Updating Notifiers (ConfirmationEmailNotifier, etc.) to use DTOs and their build() method.

When NOT to Use

• Marketing emails or newsletters (handled by another system).
• Purely static templates (no Twig variables: no {{ var }}, no {% if var %}, no parameters received via include).
• Modifying an existing .html.twig template that is not being migrated (do not break existing emails).