Changes to POST `/api/v0/files/answer-uploads/:exercise_task_id` Used to upload the files a student is attaching to an answer for the given exercise task. Unlike `POST /api/v0/files/:exercise_service_slug` this binds every stored file to the uploader and the task's exercise, which is what lets a later submission verify that the answer only names files the submitter uploaded for that exercise. # Returns An ordered list of `file_uploads` ids and stored URLs, in the order the parts were sent.