PayPal /v2/checkout/orders patch custom_id (update order)

When updating a PayPal order using the REST API, we typically do it as below according to the documentation at https://developer.paypal.com/docs/api/orders/v2/#orders_patch

curl -v -X PATCH https://api-m.sandbox.paypal.com/v2/checkout/orders/5O190127TN364715T \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer access_token' \
-d '[
  {
    "op": "add",
    "path": "/purchase_units/@reference_id==\'PUHF\'/shipping/address",
    "value": {
      "address_line_1": "2211 N First Street",
      "address_line_2": "Building 17",
      "admin_area_2": "San Jose",
      "admin_area_1": "CA",
      "postal_code": "95131",
      "country_code": "US"
    }
  }
]' 

However when trying to update the custom_id or invoice_id, it gives a validation error when trying to put a value in the "value" key since these do not represent an object like the example above. I've tried using the key "integration_artifact" as seen in an example at https://developer.paypal.com/docs/multiparty/checkout/advanced/customize/update-order-details/ but this results in an error as well

curl -v -X PATCH https://api-m.sandbox.paypal.com/v2/checkout/orders/5O190127TN364715T \
-H 'Content-Type: application/json' \
-H 'Authorization: Bearer access_token' \
-d '[
  {
    "op": "replace",
    "path": "/purchase_units/@reference_id==\'PUHF\'/custom_id",
    "value": {
      "integration_artifact": "CUSTOM_ID"
    }
  }
]' 

The error

{
  "name": "UNPROCESSABLE_ENTITY",
  "details": [
    {
      "issue": "VALIDATION_ERROR",
      "links": [],
      "description": "VALIDATION_ERROR"
    }
  ],
  "message": "The requested action could not be performed, semantically incorrect, or failed business validation.",
  "debug_id": "fca96d06c1409",
  "links": [
    {
      "href": "https://developer.paypal.com/docs/api/orders/v2/#error-VALIDATION_ERROR",
      "rel": "information_link"
    }
  ]
}

What should I put in the value for custom_id/invoice_id when the value should just be a string?

Set the value to the desired string...:

[
  {
    "op": "replace",
    "path": "/purchase_units/@reference_id=='PUHF'/custom_id",
    "value": "CUSTOM_ID"
  }
]