defp update_env(group, key, nil), do: Application.delete_env(group, key)
defp update_env(group, key, value), do: Application.put_env(group, key, value)
defp update_env(group, key, nil), do: Application.delete_env(group, key)
defp update_env(group, key, value), do: Application.put_env(group, key, value)