Fix user attribute merging to preserve all fields from users.nix

[Copilot]

The user merging logic in hosts/user-config.nix was discarding fields from the base user object (like hashedPassword, opensshKeys, enable, editor, isNormalUser) when merging with external module options.

Changed:

• Start with base user object instead of creating new attribute set with only select fields
• Overlay mkDefault wrappers for overridable fields (description, shell, extraGroups)
• Apply external module options last to maintain precedence

Before:

ugaif.users = lib.mapAttrs (name: user:
  {
    description = lib.mkDefault (user.description or null);
    shell = lib.mkDefault (user.shell or null);
    extraGroups = lib.mkDefault (user.extraGroups or [ ]);
    external = user.external or null;
  }
  // (externalUserOptions.${name} or { })
) accounts;

After:

ugaif.users = lib.mapAttrs (name: user:
  user
  // {
    description = lib.mkDefault (user.description or null);
    shell = lib.mkDefault (user.shell or null);
    extraGroups = lib.mkDefault (user.extraGroups or [ ]);
  }
  // (externalUserOptions.${name} or { })
) accounts;

All fields from users.nix now propagate to the final user configuration regardless of whether the external module defines them.

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.