vaccins/lib/vaccins_web/plugs.ex

defmodule VaccinsWeb.Plugs do
  import Plug.Conn

  def set_local_conn(conn = %{remote_ip: {ip1, _, _, _}}, opts) do
    is_local? = ip1 in [192, 127]
    conn |> assign(:is_local?, is_local?) |> put_session(:is_local?, is_local?)
  end
end