curl --request POST \
  --url http://localhost:3000/api/user/files \
  --header 'Content-Type: multipart/form-data' \
  --header 'x-access-token: <api-key>' \
  --form files='@example-file' \
  --form 'selectedCourse={
  "course_id": 123,
  "course_name": "<string>",
  "assistant": {
    "_id": "<string>",
    "name": "<string>"
  }
}'

{
  "success": true,
  "message": "<string>",
  "fileId": "<string>"
}