Create entries in msgs table for MDNs

At least one entry is required for DeleteMsgOnImap job. Additionally,
adding a hidden entry makes it possible to avoid redownloading the
message if it gets a new UID on the server.

src/dc_receive_imf.rs

@@ -624,10 +624,13 @@ fn add_parts(
             let subject = mime_parser.get_subject().unwrap_or_default();
 
             for part in mime_parser.parts.iter_mut() {
-                if mime_parser.location_kml.is_some()
+                let is_mdn = !mime_parser.reports.is_empty();
+
+                let is_location_kml = mime_parser.location_kml.is_some()
                     && icnt == 1
-                    && (part.msg == "-location-" || part.msg.is_empty())
+                    && (part.msg == "-location-" || part.msg.is_empty());
-                {
+
+                if is_mdn || is_location_kml {
                     *hidden = true;
                     if state == MessageState::InFresh {
                         state = MessageState::InNoticed;

src/mimeparser.rs

@@ -544,6 +544,16 @@ impl MimeMessage {
                             if let Some(report) = self.process_report(context, mail)? {
                                 self.reports.push(report);
                             }
+
+                            // Add MDN part so we can track it, avoid
+                            // downloading the message again and
+                            // delete if automatic message deletion is
+                            // enabled.
+                            let mut part = Part::default();
+                            part.typ = Viewtype::Unknown;
+                            self.parts.push(part);
+
+                            any_part_added = true;
                         } else {
                             /* eg. `report-type=delivery-status`;
                             maybe we should show them as a little error icon */
@@ -1344,7 +1354,7 @@ Disposition: manual-action/MDN-sent-automatically; displayed\n\
             Some("Chat: Message opened".to_string())
         );
 
-        assert_eq!(message.parts.len(), 0);
+        assert_eq!(message.parts.len(), 1);
         assert_eq!(message.reports.len(), 1);
     }
 
@@ -1422,7 +1432,7 @@ Disposition: manual-action/MDN-sent-automatically; displayed\n\
             Some("Chat: Message opened".to_string())
         );
 
-        assert_eq!(message.parts.len(), 0);
+        assert_eq!(message.parts.len(), 2);
         assert_eq!(message.reports.len(), 2);
     }
 
@@ -1467,7 +1477,7 @@ Additional-Message-IDs: <foo@example.com> <foo@example.net>\n\
             Some("Chat: Message opened".to_string())
         );
 
-        assert_eq!(message.parts.len(), 0);
+        assert_eq!(message.parts.len(), 1);
         assert_eq!(message.reports.len(), 1);
         assert_eq!(message.reports[0].original_message_id, "foo@example.org");
         assert_eq!(