curl --request PATCH \
  --url https://v1.api.flux-os.com/contracts/{id}/paper/{paper_id} \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --header 'x-user-id: <api-key>' \
  --data '
{
  "paper_from": "<unknown>",
  "governing_gtc": "<unknown>",
  "external_id": null
}
'

{
  "id": "<string>",
  "external_id": null,
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "legal_provisions": [
    {
      "id": "<string>",
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    }
  ],
  "pricing_provisions": [
    {
      "id": "<string>",
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    }
  ]
}