Introducing an Order model, and a Register module that encapsulates the logic around turning a Cart into an Order. Also, a brief introduction to Ecto transactions.
Adding the ability for the Register to charge a credit card for the Order via the Stripe API.
ExUnit; Building an example module via TDD; Exercism.io; DocTests
Defining the bottom game board boundary and providing the next shape when needed.
Simplified generation of generic servers.