- Added new API endpoints for sending, rescheduling, and canceling scheduled outbox messages.
- Implemented outbox processing logic to handle attachments and manage message statuses.
- Introduced a dead-letter strategy for failed outbox messages, enhancing reliability.
- Updated database schema to support new outbox statuses and dead-letter entries.
- Enhanced unit tests for outbox functionalities, ensuring robust error handling and validation.
- Improved attachment handling in the outbox processor to support inline and regular attachments.
- Introduced new functionality for managing email attachments and drafts in the mail API.
- Added handlers for listing, uploading, and downloading message attachments in `internal/api/mail/handlers_attachments.go`.
- Implemented draft management endpoints for creating, updating, and deleting drafts in `internal/api/mail/handlers_drafts.go`.
- Created new service methods for handling draft and attachment operations in `internal/api/mail/drafts.go` and `internal/api/mail/storage.go`.
- Added validation and error handling for draft and attachment operations.
- Included unit tests for draft and folder functionalities in `internal/api/mail/drafts_test.go` and `internal/api/mail/folders_test.go`.
- Updated API routes to support new draft and attachment features, enhancing overall mail management capabilities.
