Bug: submissions without a file extension are silently dropped
Description
Sometimes, students submit files without an extension. This should be possible, but AuTA wants an extension so that it can rename the file while retaining file format information.
Ideally, the file management portion of AuTA is reworked so that submissions have their own folder instead of a single file, so that submitted files can retain their original name.
Priority
High - students are getting "no grade"s on Submit because of this.
Definition of done
Students can submit files without a file extension.