implemented bamboo mailer, satisfying tests

lib/bones73k_web/controllers/user_registration_controller.ex

@@ -13,7 +13,7 @@ defmodule Bones73kWeb.UserRegistrationController do
   def create(conn, %{"user" => user_params}) do
     case Accounts.register_user(user_params) do
       {:ok, user} ->
-        {:ok, _} =
+        %Bamboo.Email{} =
           Accounts.deliver_user_confirmation_instructions(
             user,
             &Routes.user_confirmation_url(conn, :confirm, &1)