In the code sample for auth /pento/lib/pento_web/live/user_auth_live.ex the on_mount function is defined as:
on_mount(_, params, %{"user_token" => user_token} = _session, socket)
It seems the the params argument is never used so could be replaced with _params while the assignment to _session seems unnecessary so we end up with:
on_mount(_, _params, %{"user_token" => user_token}, socket)