server: poll for new messages and update clients via WS

notmuch/src/lib.rs

@@ -470,7 +470,7 @@ pub enum NotmuchError {
     MailParseError(#[from] mailparse::MailParseError),
 }
 
-#[derive(Default)]
+#[derive(Clone, Default)]
 pub struct Notmuch {
     config_path: Option<PathBuf>,
 }