feat: Use "From" address instead of "" as a fallback contact display …

…name (#5184)

If we cannot use the display name from the "From" header for a new contact, e.g. for mailing list
messages, use the "From" address, it's better than an empty string.

src/receive_imf.rs

@@ -601,7 +601,12 @@ pub async fn from_field_to_contact_id(
     prevent_rename: bool,
 ) -> Result<Option<(ContactId, bool, Origin)>> {
     let display_name = if prevent_rename {
-        Some("")
+        Some(
+            match Contact::lookup_id_by_addr(context, &from.addr, Origin::Unknown).await? {
+                None => from.addr.as_str(),
+                Some(_) => "",
+            },
+        )
     } else {
         from.display_name.as_deref()
     };

src/receive_imf/tests.rs

@@ -978,6 +978,16 @@ Hello mailinglist!\r\n"
     let chat = chat::Chat::load_from_db(&t.ctx, chat_id).await?;
     assert!(chat.can_send(&t.ctx).await?);
 
+    for addr in ["bob@posteo.org", "charlie@posteo.org"] {
+        let contact_id = Contact::lookup_id_by_addr(&t, addr, Origin::Unknown)
+            .await
+            .unwrap()
+            .unwrap();
+        let contact = Contact::get_by_id(&t, contact_id).await.unwrap();
+        assert_eq!(contact.get_authname(), addr);
+        assert_eq!(contact.get_display_name(), addr);
+    }
+
     Ok(())
 }