fix: check for Chat-Version header before marking the contact as a bot

Contacts are marked as a bot if incoming message from a contact
has `Auto-Submitted: auto-generated` header.
However, such message can be generated by the server,
e.g. as an auto-reply.

To prevent accidentally marking the contact as a bot
when auto-generated message is sent by the server,
we need to check for `Chat-Version` header
to make sure that the message is generated by the client.

This is already how it is documented in `MimeMessage.is_bot`
field documentation comment, but was not checked in the implementation.

src/mimeparser.rs

@@ -584,7 +584,8 @@ impl MimeMessage {
         };
 
         let is_location_only = parser.location_kml.is_some() && parser.parts.is_empty();
-        if parser.mdn_reports.is_empty()
+        if parser.has_chat_version()
+            && parser.mdn_reports.is_empty()
             && !is_location_only
             && parser.sync_items.is_none()
             && parser.webxdc_status_update.is_none()