Replace rappdirs by tools::R_user_dir()

[Bisaloo]

I see that this change was made in other r-lib repos so I thought I'd suggest it here as well.

tools::R_user_dir() was introduced in R 4.0 so safe to use with the tidyverse R version support policy/

[hadley]

I think this probably needs a bit more thought than in other packages, because we'd need to make sure that this directory eventually gets cleaned up.

[Bisaloo]

But I don't see any mechanism in rappdirs to clean up. My understanding is that the user or the OS takes care of this. In which case, the situation should be the same with the folder created by tools::R_user_dir().

As far as I understand, the main difference between rappdirs and tools::R_user_dir() is that rappdirs covers the different cases (config, cache, etc.) via different functions while tools::R_user_dir() does it via its which argument.

Am I missing something?

[hadley]

httr2 has cache_disk_prune() which is called automatically on load, and ensures that all tokens > 30 days old are deleted. These tokens can be used to do stuff on your behalf so I wanted to avoid having them lay around for an unlimited amount of time.

[hadley]

Ok, I've implemented what I think is needed. I just need to think through if it's ok for this to go in a patch release.

[hadley]

I think this is probably safe for a patch release, but I just feel weird about moving these high security files without more info, i.e. the blog post that will come with a minor release. So I'm going to hold off until httr2 does its next minor release.