Permanently deletes one or more files
This call will recursively delete files if needed. It is possible that a provider might fail to
completely delete the entire sub-tree. This can, for example, happen because of a crash or because the
file-system is unable to delete a given file. This will lead the file-system in an inconsistent state.
It is not guaranteed that the provider will be able to detect this error scenario. A client of the
API can check if the file has been deleted by calling
retrieve on the file.