curl --request POST \
  --url https://api.tread-horizon.com/v1/loads/{load-id}/file_attachments \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'file=<string>' \
  --form category=Other \
  --form 'description=<string>' \
  --form file.0='@example-file'

{
  "data": {
    "category": "Other",
    "description": "<string>",
    "file_attachable_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "file_url": "<string>",
    "mime_type": "<string>",
    "preview_url": "<string>",
    "preview_mime_type": "<string>",
    "uploaded_by": {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "tread_id": "ABC123",
      "legal_name": "<string>",
      "company_type": "hauler"
    },
    "file_name": "<string>",
    "editable": true,
    "deletable": true,
    "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "created_at": "2023-11-07T05:31:56Z",
    "updated_at": "2023-11-07T05:31:56Z"
  }
}