Set Shipping Method

curl --request POST \
  --url https://api.firmly.work/api/v1/domains/staging.luma.gift/cart/shipping-method \
  --header 'x-firmly-authorization: YOUR_TOKEN' \
  --header 'Content-Type: application/json' \
  --data '{"shipping_method": "express_2day"}'

{
  "cart_id": "1e43868c-d4a5-418c-bd6b-5fff043550d2",
  "platform_id": "example",
  "shop_id": "staging.luma.gift",
  "display_name": "Luma Store",
  "line_items": [
    {
      "line_item_id": "1ee530e1-063d-4e07-afb2-e7e65245977e",
      "sku": "WS12-XS-Orange",
      "quantity": 1,
      "description": "Radiant Tee - Orange XS",
      "price": {
        "currency": "USD",
        "value": 22.00,
        "symbol": "$",
        "number": 2200
      },
      "line_price": {
        "currency": "USD",
        "value": 22.00,
        "symbol": "$",
        "number": 2200
      }
    }
  ],
  "shipping_info": {
    "first_name": "John",
    "last_name": "Smith",
    "email": "john@staging.luma.gift",
    "address1": "123 Main St",
    "city": "Seattle",
    "postal_code": "98101",
    "state_or_province": "Washington",
    "country": "United States"
  },
  "shipping_method": {
    "sku": "express_2day",
    "description": "Express 2-Day",
    "price": {
      "currency": "USD",
      "value": 19.99,
      "symbol": "$",
      "number": 1999
    }
  },
  "sub_total": {
    "currency": "USD",
    "value": 869.99,
    "symbol": "$",
    "number": 86999
  },
  "shipping_total": {
    "currency": "USD",
    "value": 19.99,
    "symbol": "$",
    "number": 1999
  },
  "tax": {
    "currency": "USD",
    "value": 4.40,
    "symbol": "$",
    "number": 440
  },
  "total": {
    "currency": "USD",
    "value": 46.39,
    "symbol": "$",
    "number": 4639
  }
}