`dunai`: Implement `ListT` interface using `list-transformer`

[ivanperez-keera]

The current module exporting functions to work with the ListT monad relies on an implementation of ListT that is outdated and has been removed from newer versions of the transformers library.

Following the discussion in #368, it seems like we could replace it with the implementation in list-transformer.

[ivanperez-keera]

Pinging @madjestic @nullobject @turion @tomsmeding @DrewFenwick as participants in the original discussion. Please feel free to try the solution proposed in branch https://github.com/ivanperez-keera/dunai/tree/develop-list-transformer. The export and the dependency are controlled with a flag list-transformer.

[nullobject]

@ivanperez-keera I have tested the proposed branch in my project and it compiles no problem (I'm using Stack LTS 22.23) 🎉

This is great, because I previously couldn't even compile dunai with stack's newer version of transformers. Hopefully this also means we can get dunai included in stack's packages again.

If you cut a new release of dunai, will this change still be behind a flag?

[ivanperez-keera]

Thanks for trying it! Great to hear that it compiles.

Because this is an API-breaking change, my plan is to put it behind a flag for the next two versions and deprecate the older interface. On the third version released from now, the old interface will be removed and only the new one remain (that'll be the release coming out on October 21, 2024).

The flag has manual set to False, so that the flag itself can automatically take the value True if needed to install with transformers > 0.6. Cabal has no problems dealing with that automatically.