Can't set absolute path in `containers.<name>.bindMounts.mountPoint` without impurity

Hi, I’m trying to setup a nixos-container by trying to use the containers module.

But if I have the following option in my config:

    bindMounts.token = {
      hostPath = config.age.secrets.github-nix-ci.path;
      isReadOnly = true;
      mountPoint = "/mnt/token";
    };

then I’m getting the following error message if I try to deploy my confi:

       error: access to absolute path '/mnt/token' is forbidden in pure eval mode (use '--impure' to override)

Shouldn’t this be still accepted since the absolute path is just within the container or do I really have to use --impure here?

I fixed it by using the official service for that: NixOS Search