feat: support attachments when composing mail

[bastigfz]

No description provided.

[Copilot]

🟡 Changes recommended

There are correctness issues in the mail route spec generation (z.toJSONSchema usage) and in the send flow where a null SMTP result can still return HTTP 200.

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Pull request overview

This PR adds support for composing and sending emails with attachments by accepting multipart/form-data on the mail creation endpoint, enforcing a configurable total attachment size limit, and ensuring draft sending relays the stored raw RFC822 source to preserve MIME structure.

Changes:

• Add multipart/form-data support for POST .../mails with attachment ingestion and a max combined attachment size limit (DLA_MAX_ATTACHMENT_SIZE_MB).
• Send drafts via SMTP using the exact stored message source (IMAPAccount.getMailSource() + SMTPAccount.sendRaw()), preserving attachments/inline parts.
• Extend test coverage to validate multipart attachment creation and document the new env var in example.env.

File summaries

File	Description
tests/helpers/preload.ts	Sets DLA_MAX_ATTACHMENT_SIZE_MB for the test environment.
tests/api.routes.test.ts	Adds an integration test that creates a multipart draft with an attachment and verifies attachment metadata.
src/utils/mails/backends/smtp.ts	Adds sendRaw() to relay a stored RFC822 source via SMTP with an explicit envelope.
src/utils/mails/backends/imap.ts	Adds getMailSource() to fetch a message’s raw RFC822 source from IMAP.
src/utils/config.ts	Registers DLA_MAX_ATTACHMENT_SIZE_MB in the config schema.
src/api/versions/v1/routes/mail-accounts/mailboxes/mails/model.ts	Defines an OpenAPI schema for multipart create-mail requests with attachments.
src/api/versions/v1/routes/mail-accounts/mailboxes/mails/index.ts	Implements multipart parsing, size limiting, MailComposer attachment wiring, and raw-source sending for drafts.
example.env	Documents DLA_MAX_ATTACHMENT_SIZE_MB and its default.

Review details

Suppressed comments (1)

src/api/versions/v1/routes/mail-accounts/mailboxes/mails/index.ts:176

• z.toJSONSchema(...) is not used anywhere else in the repo and is likely not available on the Zod export; this can break OpenAPI generation or compilation. Use resolver(MailsModel.Create.Body) (from hono-openapi) for consistency with the rest of the API spec helpers.

                "application/json": { schema: z.toJSONSchema(MailsModel.Create.Body) as OpenAPIV3_1.SchemaObject },

• Files reviewed: 8/8 changed files
• Comments generated: 3
• Review effort level: Lite

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