feat(api): parse username and email

- Updated cargo deps

src/domain/mod.rs

@@ -0,0 +1,7 @@
+mod new_subscriber;
+mod subscriber_email;
+mod subscriber_name;
+
+pub use new_subscriber::NewSubscriber;
+pub use subscriber_email::SubscriberEmail;
+pub use subscriber_name::SubscriberName;