Fix cargo clippy issues

src/main.rs

@@ -51,7 +51,7 @@ async fn main() -> std::io::Result<()> {
 
     // Create initial user if required
     if users.is_empty() {
-        log::info!("Create default {} user", DEFAULT_ADMIN_USERNAME);
+        log::info!("Create default {DEFAULT_ADMIN_USERNAME} user");
         let default_admin = User {
             username: DEFAULT_ADMIN_USERNAME.to_string(),
             authorized_clients: None,