add trait impl back in

Author: Dav1dde

develop-docs/engineering-practices/rust.mdx

@@ -57,6 +57,12 @@ and should generally be preferred now.
 pub trait Database {
     fn get_user(&self) -> impl Future<Output = User> + Send;
 }
+
+impl Database for MyDatabase {
+    async fn get_user(&self) -> User {
+        todo!()
+    }
+}
 ```
 
 Note that the returned future type is `Send`, to ensure that it can run on a multi-threaded runtime.