This attribute is a generalized version of cryptHomeLuks for creating an
entry in /etc/security/pam_mount.conf.xml. It lets the configuration
control all the attributes of the entry, instead of just the
path. The default path remains the value of cryptHomeLuks, for
compatibility.

Motivation for this change

I'd like to configure pam_mount with more control than the existing cryptHomeLuks attribute allows, specifically adding options.
pam_mount isn't specific to luks or block devices, and it's easy to expose basically all of its features by allowing any attributes here.

For example, my local user now looks like:

  users.users.dnr = {
    ...
    pamMount = {
      path = "/dev/disk/by-uuid/42be38bf-a911-4940-b9ab-e0f640cae689";
      options = "crypto_name=home,noatime,compress-force=zstd";
    };
  };

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.