Where should I create temporary directories in an app?

I'm developing a Shiny app using a package structure. To use the app, users will have to upload compressed files (usually of a few Go in size) that will be preprocessed internally and dumped once the preprocess stage is over.

I'm thinking of storing those files temporarily using withr::local_tempdir(). My question is : where should the temp dir live? In a server function or in the namespace of the package?