curl --request POST \
  --url https://api.example.com/api/playground/sessions/{session_id}/upload \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form file='@example-file'

{
  "id": "<string>",
  "name": "<string>",
  "source": "<string>",
  "status": "<string>",
  "progress": 123,
  "created_at": "<string>",
  "updated_at": "<string>",
  "source_ref": "<string>",
  "row_count": 123,
  "column_count": 123,
  "columns": [],
  "file_size_bytes": 123,
  "file_names": [
    "<string>"
  ],
  "error_message": "<string>",
  "cancel_requested": false
}