Updates the CartItem resource.

curl -X PATCH "/api/cart_items/{id}" \
  -H "apikey: $MEDIALISTER_API_KEY" \
  -H "Content-Type: application/merge-patch+json" \
  -d '{
  "campaign": "/api/campaigns/abcd32bd-a699-4f3e-bb19-ea807a0a6fc8",
  "excluded": false
}'

{
  "@context": "string",
  "@id": "string",
  "@type": "string",
  "product": {
    "@context": "string",
    "@id": "string",
    "@type": "string",
    "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "formatType": "/api/format_types/b64ed0ca-1a05-4898-9a52-765fed38bc5c",
    "mediaProject": "/api/media_projects/b64ed0ca-1a05-4898-9a52-765fed38bc5c",
    "price": 100.1,
    "desiredPrice": "string",
    "urlExamples": [
      "string"
    ],
    "currency": "/api/currencies/b64ed0ca-1a05-4898-9a52-765fed38bc5c",
    "listed": false,
    "byRequest": false,
    "turnAroundTime": 0,
    "notificationsCount": 0,
    "createdAt": "2026-01-15T09:30:00Z",
    "updatedAt": "2026-01-15T09:30:00Z",
    "numericPrice": 0,
    "visible": true,
    "createdAtTimestamp": 0,
    "updatedAtTimestamp": 0,
    "status": 0
  },
  "price": "string",
  "currency": {
    "@context": "string",
    "@id": "string",
    "@type": "string",
    "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "name": "string",
    "symbol": "string",
    "type": "fiat",
    "decimals": 2
  },
  "cart": "https://example.com/",
  "flatFee": "string",
  "minFee": "string",
  "feePercent": "string",
  "campaign": {
    "@context": "string",
    "@id": "string",
    "@type": "string",
    "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "name": "Campaign Name",
    "goal": "My Goal",
    "goalDetails": "seo-in-new-articles",
    "domain": "string",
    "budget": 0,
    "publishingPeriod": 0,
    "regions": [
      "dXJuOm1ieHBsYzpSRUk",
      "dXJuOm1ieHBsYzpSRUd"
    ],
    "notificationsCount": 0,
    "createdAt": "2026-01-15T09:30:00Z",
    "updatedAt": "2026-01-15T09:30:00Z"
  },
  "excluded": false,
  "cartItemExtras": [
    {
      "@context": "string",
      "@id": "string",
      "@type": "string",
      "extra": {
        "@context": "string",
        "@id": "string",
        "@type": "string",
        "description": "string",
        "conditions": {
          "key": "string"
        },
        "name": "string",
        "currency": {
          "@context": "string",
          "@id": "string",
          "@type": "string",
          "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
          "name": "string",
          "symbol": "string",
          "type": "fiat",
          "decimals": 2
        },
        "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
        "createdAt": "2026-01-15T09:30:00Z",
        "updatedAt": "2026-01-15T09:30:00Z"
      },
      "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
      "createdAt": "2026-01-15T09:30:00Z",
      "updatedAt": "2026-01-15T09:30:00Z",
      "price": {}
    }
  ],
  "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
  "createdAt": "2026-01-15T09:30:00Z",
  "updatedAt": "2026-01-15T09:30:00Z"
}