- Added `sendWashCertificateToCustomer` method in `order_bookings_o` to handle email sending for wash certificates.
- Implemented `sendWashCertificateEmailToCustomer` in `email` to generate and attach wash certificate PDFs.
- Updated attachment permission logic in `ordersRoute` and `db_object_t`.
- Changed `object_attachments_o` property types and handling for improved attachment processing.