user_controller.ex

def create(conn, %{"user" => user_params}) do
  changeset = User.registration_changeset(%User{}, user_params)

  case Repo.insert(changeset) do
    { :ok, user } ->
      conn
      |> Rumbl.Auth.login(user)
      |> put_flash(:info, "#{user.name} created!")
      |> redirect(to: user_path(conn, :index))
    { :error, changeset } ->
      render(conn, "new.html", changeset: changeset)
  end
end