Add payment guards to your routes or controllers!

Examples:

defmodule MyAppWeb.AdminLinkController do
  use MyAppWeb, :controller
  require Logger

  plug Shopifex.Plug.PaymentGuard, "premium_plan" when action in [:premium_function]

  def premium_function(conn, _params) do
    # Wow, much premium.
    conn
    |> send_resp(200, "success")
  end
end