Affirm client library for Elixir.

For api reference, please visit: https://docs.affirm.com/Integrate_Affirm/Direct_API

Defines a __using__ macro for ease of use inside implementation modules For example:

defmodule AffirmService do
  use Affirm

  def attempt_capture(charge_id) do
    case capture(charge_id) do
      {:ok, response} -> # do success things
      {:error, message} -> # do failure things
    end
  end
end