v0.3.12
Make subscriber name optional, bump version to 0.3.12 to match Listmonk API/UI behavior (fixes #15)
This update aligns the SDK with the Listmonk API and UI by making the name field optional for
subscribers. The change propagates through the data models (Subscriber, CreateSubscriberModel)
and the create_subscriber() helper. The changelog is updated to reflect version 0.3.12, and the
release comparison links are adjusted accordingly.