add test with multiple text parts

the test has multiple text parts because
the content text is signed and
the mailinglist software wants to add some text
(and cannot alter signed part without breaking the signature)

src/dc_receive_imf.rs

@@ -3156,6 +3156,31 @@ mod tests {
         assert_eq!(chat.name, "Intern");
     }
 
+    #[async_std::test]
+    async fn test_mailing_list_with_mimepart_footer_signed() {
+        let t = TestContext::new_alice().await;
+        t.set_config(Config::ShowEmails, Some("2")).await.unwrap();
+
+        dc_receive_imf(
+            &t,
+            include_bytes!("../test-data/message/mailinglist_with_mimepart_footer_signed.eml"),
+            "INBOX",
+            1,
+            false,
+        )
+        .await
+        .unwrap();
+        let msg = t.get_last_msg().await;
+        assert_eq!(get_chat_msgs(&t, msg.chat_id, 0, None).await.len(), 1);
+        let text = msg.text.clone().unwrap();
+        assert!(text.contains("content text"));
+        assert!(!text.contains("footer text"));
+        assert!(msg.has_html());
+        let html = msg.get_id().get_html(&t).await.unwrap();
+        assert!(html.contains("content text"));
+        assert!(!html.contains("footer text"));
+    }
+
     #[async_std::test]
     async fn test_dont_show_tokens_in_contacts_list() {
         check_dont_show_in_contacts_list(

test-data/message/mailinglist_with_mimepart_footer_signed.eml

@@ -0,0 +1,80 @@
+Return-Path: <intern-bounces@lists.abc.de>
+X-Original-To: bp@def.com
+Delivered-To: m1234567@dd12345.kasserver.com
+X-policyd-weight: using cached result; rate: -6.1
+Received: from mail.alfi.li (mail.alfi.li [85.14.254.25])
+	by dd12345.kasserver.com (Postfix) with ESMTPS id 123456789598
+	for <bp@def.com>; Wed,  3 Mar 2021 01:01:25 +0100 (CET)
+To: intern@lists.abc.de
+References: <12345678-1234-1234-1234-123456789012@mr.de>
+From: mr <mr@mr.de>
+Message-ID: <22222222-2222-2222-2222-222222222222@mr.de>
+Date: Wed, 3 Mar 2021 01:01:11 +0100
+In-Reply-To: <12345678-1234-1234-1234-123456789012@mr.de>
+Subject: Re: [Intern] more important stuff
+X-BeenThere: intern@lists.abc.de
+X-Mailman-Version: 2.1.29
+Precedence: list
+List-Id: <intern.lists.abc.de>
+List-Unsubscribe: <http://lists.abc.de/mailman/options/intern>,
+ <mailto:intern-request@lists.abc.de?subject=unsubscribe>
+List-Archive: <http://lists.abc.de/mailman/private/intern/>
+List-Post: <mailto:intern@lists.abc.de>
+List-Help: <mailto:intern-request@lists.abc.de?subject=help>
+List-Subscribe: <http://lists.abc.de/mailman/listinfo/intern>,
+ <mailto:intern-request@lists.abc.de?subject=subscribe>
+Content-Type: multipart/mixed; boundary="===============1234567890253566549=="
+Errors-To: intern-bounces@lists.abc.de
+Sender: "Intern" <intern-bounces@lists.abc.de>
+
+This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
+--===============1234567890253566549==
+Content-Type: multipart/signed; micalg=pgp-sha256;
+ protocol="application/pgp-signature";
+ boundary="2222222222nheMkezDtEaCy2H1M0Q3wtX"
+
+This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
+--2222222222nheMkezDtEaCy2H1M0Q3wtX
+Content-Type: multipart/mixed; boundary="kpbXdSJRuZxNyB43gEja0tpvinYpituTJ";
+ protected-headers="v1"
+From: mr <mr@mr.de>
+To: intern@lists.abc.de
+Message-ID: <22222222-2222-2222-2222-222222222222@mr.de>
+Subject: Re: more important stuff
+References: <12345678-1234-1234-1234-123456789012@mr.de>
+In-Reply-To: <12345678-1234-1234-1234-123456789012@mr.de>
+
+--kpbXdSJRuZxNyB43gEja0tpvinYpituTJ
+Content-Type: text/plain; charset=utf-8
+Content-Language: en-US
+Content-Transfer-Encoding: quoted-printable
+
+On 02.03.21 22:41, mr wrote:
+> quote to trigger has_html
+
+content text
+
+--kpbXdSJRuZxNyB43gEja0tpvinYpituTJ--
+
+--2222222222nheMkezDtEaCy2H1M0Q3wtX
+Content-Type: application/pgp-signature; name="OpenPGP_signature.asc"
+Content-Description: OpenPGP digital signature
+Content-Disposition: attachment; filename="OpenPGP_signature"
+
+-----BEGIN PGP SIGNATURE-----
+
+ws1234567890FiEEiGlkiQz18Vyq7pbiOWr31234567890A+0ccFAwAAAAAACgkQOWr3EM0fY5yc=
+=oIB5
+-----END PGP SIGNATURE-----
+
+--2222222222nheMkezDtEaCy2H1M0Q3wtX--
+
+--===============1234567890253566549==
+Content-Type: text/plain; charset="us-ascii"
+Content-Transfer-Encoding: 7bit
+Content-Disposition: inline
+
+footer text
+
+--===============1234567890253566549==--
+