Ignore Drafts folder when scanning (#2454)

* Add failing test for #2369

* Completely ignore Drafts folder

fix #2369

* Also ignore messages that have the Draft flag set but are not in the Drafts folder

src/dc_receive_imf.rs

@@ -2742,11 +2742,14 @@ mod tests {
 
         // Check that the ndn would be downloaded:
         let headers = mailparse::parse_mail(raw_ndn).unwrap().headers;
-        assert!(
-            crate::imap::prefetch_should_download(&t, &headers, ShowEmails::Off)
-                .await
-                .unwrap()
-        );
+        assert!(crate::imap::prefetch_should_download(
+            &t,
+            &headers,
+            std::iter::empty(),
+            ShowEmails::Off
+        )
+        .await
+        .unwrap());
 
         dc_receive_imf(&t, raw_ndn, "INBOX", 1, false)
             .await