Store data in the private directory

Problem/Motivation

Steps to reproduce

StructureMapFilterFormExport: exporting to the public file system is not ideal, because then you are showing that to any user? I think it is not a security issue because there is no secret data in the structure of your entity and fields? Ideally you would export to private files, then only authorized users can download the export file.
The export files are never deleted? That could clutter disk space, probably makes sense to cleanup somewhere.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes