Delete messages to the Trash folder for Gmail by default (#3957)

Gmail archives messages marked as `\Deleted` by default if those messages aren't in the Trash. But
if move them to the Trash instead, they will be auto-deleted in 30 days.

src/ephemeral.rs

@@ -588,19 +588,25 @@ pub(crate) async fn delete_expired_imap_messages(context: &Context) -> Result<()
                 now - max(delete_server_after, MIN_DELETE_SERVER_AFTER),
             ),
         };
+    let target = context.get_delete_msgs_target().await?;
 
     context
         .sql
         .execute(
             "UPDATE imap
-             SET target=''
+             SET target=?
              WHERE rfc724_mid IN (
                SELECT rfc724_mid FROM msgs
                WHERE ((download_state = 0 AND timestamp < ?) OR
                       (download_state != 0 AND timestamp < ?) OR
                       (ephemeral_timestamp != 0 AND ephemeral_timestamp <= ?))
              )",
-            paramsv![threshold_timestamp, threshold_timestamp_extended, now],
+            paramsv![
+                target,
+                threshold_timestamp,
+                threshold_timestamp_extended,
+                now,
+            ],
         )
         .await?;