Django-file-form

- Issue 422: add model rename to migrations (thanks to Shrikrishna Singh)

- Issue 418: correctly remove upload

- Issue 388: add cross-site request forgery protection to tus uploads using the standard Django csrf token
- Issue 393: fix delete-unused-files command (thanks to Seb Haase)
- issue 401: optimization: use move instead of copy when possible

- Issue 324: get placeholder file for UploadWidget (thanks to Shrikrishna Singh)
- Issue 330: allow upload directly to S3 compatible storages (thanks to Bo Peng)
- Issue 331: fix error in deleting files (thanks to Bo Peng)
- Issue 333: replace existing uploaded file with the same name (thanks to Bo Peng)
- Issue 341: add javascript events (experimental)
- Issue 346: allow definition of s3_upload_dir in form class (thanks to Bo Peng)

- Issue 347: add chunkSize parameter to avoid request error in Django

- Issue 320: fix UploadMultipleWidget to return correct placeholder files (thanks to Shrikrishna Singh)
- Issue 325: support Django 3.1