Update rust-email, test that no empty lines are produced (#2119)

* Add a failing test for #2118

* Update rust-email to fix #2118

src/mimefactory.rs

@@ -1618,4 +1618,56 @@ mod tests {
             .await
             .unwrap();
     }
+
+    #[test]
+    fn test_no_empty_lines_in_header() {
+        // See https://github.com/deltachat/deltachat-core-rust/issues/2118
+        let to_tuples = [
+            ("Nnnn", "nnn@ttttttttt.de"),
+            ("😀 ttttttt", "ttttttt@rrrrrr.net"),
+            ("dididididididi", "t@iiiiiii.org"),
+            ("Ttttttt", "oooooooooo@abcd.de"),
+            ("Mmmmm", "mmmmm@rrrrrr.net"),
+            ("Zzzzzz", "rrrrrrrrrrrrr@ttttttttt.net"),
+            ("Xyz", "qqqqqqqqqq@rrrrrr.net"),
+            ("", "geug@ttttttttt.de"),
+            ("qqqqqq", "q@iiiiiii.org"),
+            ("bbbb", "bbbb@iiiiiii.org"),
+            ("", "fsfs@iiiiiii.org"),
+            ("rqrqrqrqr", "rqrqr@iiiiiii.org"),
+            ("tttttttt", "tttttttt@iiiiiii.org"),
+            ("", "tttttt@rrrrrr.net"),
+        ]
+        .iter();
+        let to: Vec<_> = to_tuples
+            .map(|(name, addr)| {
+                if name.is_empty() {
+                    Address::new_mailbox(addr.to_string())
+                } else {
+                    Address::new_mailbox_with_name(name.to_string(), addr.to_string())
+                }
+            })
+            .collect();
+
+        let mut message = email::MimeMessage::new_blank_message();
+        message.headers.insert(
+            (
+                "Content-Type".to_string(),
+                "text/plain; charset=utf-8; format=flowed; delsp=no".to_string(),
+            )
+                .into(),
+        );
+        message
+            .headers
+            .insert(Header::new_with_value("To".into(), to).unwrap());
+        message.body = "Hi".to_string();
+
+        let msg = message.as_string();
+
+        let header_end = msg.find("Hi").unwrap();
+        #[allow(clippy::indexing_slicing)]
+        let headers = msg[0..header_end].trim();
+
+        assert!(!headers.lines().any(|l| l.trim().is_empty()));
+    }
 }