Not parsing text/plain alternative body

[mjforan]

Many apprise notifier services do not accept HTML, so it is desirable to select the text/plain body instead of text/html. The current implementation of multipart parsing does not work for me. Specifically, I am receiving emails from a Vaultwarden instance which look like this (content removed):

Message-ID: <[email protected]>
To: [email protected]
From: Vaultwarden <[email protected]>
Subject: Join Vaultwarden
MIME-Version: 1.0
Date: Sun, 15 Dec 2024 16:06:17 +0000
Content-Type: multipart/alternative;
 boundary="vgKXVg4d5YpsJGi6MgrgT0k4G2AUQeXLDzp5guXW"

--vgKXVg4d5YpsJGi6MgrgT0k4G2AUQeXLDzp5guXW
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

--vgKXVg4d5YpsJGi6MgrgT0k4G2AUQeXLDzp5guXW
Content-Type: multipart/related;
 boundary="QVY5Vete64ETsCmogCKhhgk7HyPE8GPOJYGctGrJ"

--QVY5Vete64ETsCmogCKhhgk7HyPE8GPOJYGctGrJ
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable

--QVY5Vete64ETsCmogCKhhgk7HyPE8GPOJYGctGrJ
Content-ID: <logo-gray.png>
Content-Disposition: inline
Content-Type: image/png
Content-Transfer-Encoding: base64

--QVY5Vete64ETsCmogCKhhgk7HyPE8GPOJYGctGrJ
Content-ID: <mail-github.png>
Content-Disposition: inline
Content-Type: image/png
Content-Transfer-Encoding: base64

--QVY5Vete64ETsCmogCKhhgk7HyPE8GPOJYGctGrJ--

--vgKXVg4d5YpsJGi6MgrgT0k4G2AUQeXLDzp5guXW--

The current parser only gets the multipart/related section, missing the text/plain.