Fixes programming error when delete if no data file set.
Allows create in detail view.
Removes not working overriding.
Overrides get_serializer method to ensure current default user in POST or PUT calls (works better).
Checks response data fields wisely.
Adds POST additional tests when POST on the target path directly.
Tests if upload works on POST.
Adds simple 'file exists' check before delete.
Adds simple comment.
Removes blank line.