nix-darwin: use correct username in activation script

[toodeluna]

Description

This pull request updates the nix-darwin activation script to use the correct username. This was previously not the case if the username didn't match the key in the users attribute set, e.g.:

{
  users.users.myUser = {
    name = "actual_name";
  };
}

In this case home-manager would try to run the activation script for "myUser" when it should run for "actual_name".

There's another pull-request that fixes this issue (#5881) but it got marked as stale.

Checklist

• Change is backwards compatible.
• Code formatted with ./format.

[toodeluna]

Forgot to add this to pull request, so putting it here:

Maintainer CC
@toonn @rycee

[toonn]

This is the exact same code change? At least cherry-pick their commit so they retain autorship, otherwise it's plagiarism.

There's also no point in opening a PR with the same exact change, that doesn't make it any less stale than commenting on the original PR. You should also address the comments on the original since those not being addressed is why it went stale.

[toodeluna]

I only found out there was already a PR for this after I already made these changes myself. While making this PR I thought to check if someone else had already made the change and found the previous PR with a comment from the stale-bot which says that "If you want to pick up the work on this PR, please create a new PR and indicate that it supercedes and closes this PR". Maybe I misinterpreted this, but this is one of my first contributions to an open source project so I wasn't sure about what the best way to deal with this was which is why I made the PR. I apologize if this wasn't the right way to deal with this situation.

If there's any comments that need to be addressed for this change I'll cherry-pick their commit and address them, but I'm not sure what these would be since the changes on the other PR seem to be approved (in which case I'll delete this PR and the original one can be merged instead).