Feature request: additional infos in "queue: delivered" logging

Hello,

I'm using maddy since a few days, I read about it on the [healthchecks.io blog re it's email setup](https://blog.healthchecks.io/2023/08/notes-on-self-hosted-transactional-email/), I like it.

Thank you for this!

# Use case

_What problem you are trying to solve?_

I'd like the possibility to "proof" that a remote MX has accepted the email, by logging body message ID, hostname as well as exact response.

_Note alternatives you considered and why they are not useful._

Enabling debug mode allows some correlation between a hostname and the mail delivery, however it is missing body message ID and MX response, and the hostname is only a guess based on timestamp correlation.

# Your idea for a solution

_How your solution would work in general?_

To the "queue: delivered" log I would suggest to add:

- hostname (example: `example-org.mail.protection.outlook.com`)
- body message id (example: `s0dhgv0shgherhghwsgg@thunderbird.local`)
- MX answer (example: `250 OK id=w8eghw80ehg-BW`)

Something like:

queue: delivered {"attempt":1,"msg_id":"a70cc095","body_msg_id":"s0dhgv0shgherhghwsgg@thunderbird.local","hostname":"example-org.mail.protection.outlook.com","answer":"250 OK id=w8eghw80ehg-BW","rcpt":"john@example.org"}

- [ ] I'm willing to help with the implementation
- [X] I'm willing to test with the implementation

Sorry, I'm not a go developer.

Best regards,

Lukas

まず `queue: delivered` のログ出力エントリポイントと、リモートホスト名および MX 応答を持つ配信パスを追跡します。本文メッセージ ID と配信応答がどのように表現されているかを確認し、ログに要求されたフィールドが含まれ、提案された例と一致することを確認します。

索引モデルが issue の本文から書いたものです。