curl --request PATCH \
  --url https://api.conduit.ai/v1/contacts/{id}/custom-attributes \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "attributes": [
    {
      "id": "attr_123",
      "value": "vip"
    },
    {
      "id": "attr_456",
      "value": null
    }
  ]
}
'

{
  "data": [
    {
      "id": "attr_123",
      "workspace_id": "j57demo8f8x7c9v0n2q4r6t8y1u3i5o",
      "name": "VIP Status",
      "type": "Select",
      "options": [
        {
          "value": "standard",
          "color": "gray"
        },
        {
          "value": "vip",
          "color": "green"
        }
      ],
      "order": 1,
      "section_id": "section_123",
      "section_name": "Contact Info",
      "value": "vip"
    },
    {
      "id": "attr_456",
      "workspace_id": "j57demo8f8x7c9v0n2q4r6t8y1u3i5o",
      "name": "Move-in Date",
      "type": "Date",
      "options": null,
      "order": 2,
      "section_id": "section_123",
      "section_name": "Contact Info",
      "value": null
    }
  ]
}