Improve the Content-Disposition header formatting for file downloads by implementing RFC 5987 compliant filename encoding. This ensures that downloaded files retain their original names, including spaces and non-ASCII characters, across different browsers.
- Add `contentDisposition` helper to generate both standard ASCII fallback and UTF-8 encoded filename parameters.
- Sanitize filenames to prevent path traversal and replace unsafe characters with underscores in the ASCII fallback.
- Update single file and ZIP downloads to use the new formatting.
- Add unit tests to verify correct header generation for various filename scenarios.
Daniel Legt
dbfdacc396