How can i add custom values in quote using REST api

Question

i have tried this solution Add Custom Field in Order and Quote Table To be Used in REST API. But still the custom field values are not setting in quote table. Here is my payload for POST request

<base_url>/rest/V1/carts/mine/items

Payload:

{
    "cart_item": {
        "sku": "H6S4K461FDD192",
        "qty": 1,
        "quote_id": "256",
        "product_option": {
            "extension_attributes": {      
                "custom_options":  [
                    {
                        "option_id":"374",
                        "option_value":"1522"
                    },
                    {
                        "option_id":"373",
                        "option_value":"898"
                    },
                    {
                        "option_id":"372",
                        "option_value":"895"
                    }
                ],
                "configurable_item_options": [
                    {
                        "option_id": "93",
                        "option_value": "110"
                    }
                ]
            }
        },
        "extension_attributes": {  
            "layaway":"1",
            "downpayment":"1838.00",
            "finalpayment":"1444.50",
            "duration":"30",
            "bank_name":"Bank Name",
            "layaway_multipay":"0",
            "multi_pay_initial":"0"
        }
    }
}

i want to set values of layaway,downpayment finalpayment duration bank_name layaway_multipay multi_pay_initial in quote table

i have also added extension_attributes.xml

Answer 1

Check that you have your custom attributes as columns in the quote table AND also you have a typo in your request :)

As per https://magento.redoc.ly/2.4.2-admin/#operation/quoteCartItemRepositoryV1SavePost, the key is 'cartItem', not 'cart_item'