getText/getHTML should be able to parse multipart messages

[nitzel]

It would be fantastic for testing emails if getHTML and getText would be able to parse multipart/mixed messages by actually checking the body and extracting the right part. Currently they can't find a matching header and thus abort.

Example:

Content-Type: multipart/mixed; boundary="===============7426108140616550474=="
Date: Tue, 17 May 2022 11:12:22 +0000
From: from@test.com
MIME-Version: 1.0
Message-ID: <165278594245.265.1843128869165443175@09814d7d4841>
Received: from [123.4.5.6] by mailhog.example (MailHog)
          id MNnNbGMyvWxyJ7lmXH_0e4PSTgekCuo9dFCqyxeR0QA=@mailhog.example; Tue, 17 May 2022 11:12:22 +0000
Return-Path: <from@test.com>
Subject: Some Test Subject
To: to@test.com

--===============7426108140616550474==
Content-Type: multipart/alternative;
 boundary="===============1607218409922029753=="
MIME-Version: 1.0

--===============1607218409922029753==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit


--===============1607218409922029753==
Content-Type: text/html; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Some Test MEssage
    
--===============1607218409922029753==--

--===============7426108140616550474==--