How to register webhook telegram?

Question

Node.js

The cart writes the answer that the webhook is deleted, this answer should be if you send an empty request

https://api.telegram.org/bot1111111:aaaaaaa/setWebhook

but I write from-data and put it in the body, it is logical to assume that I am not correctly forming from-data, who knows what the error is?

cart response

{ ok: true, result: true, description: 'Webhook is already deleted' }

code

var formdata = new FormData();
    //for( let key in body ) formdata.append( key, body[ key ] );

    formdata.append("url", "https://api.domain.ru/telegram/bot1111111:aaaaaaa");
    formdata.append("certificate", fs.readFileSync("/etc/api.domain.ru/cert.pem"), { filename: 'cert.pem' });

    console.log(formdata)

    var requestOptions = {
        method: 'POST',
        headers: { "Content-Type": "application/json" },
        body: formdata
    };

    fetch("https://api.telegram.org/bot1111111:aaaaaaa/setWebhook", requestOptions)
    .then(response => response.json())
    .then(result => console.log(result))
    .catch(error => console.log('error', error));

this request works fine through postman, but does not work on my server.
https is checked, the certificate is signed and works, if you connect through a third-party library, then the webhook works fine. But I need to write my own methods and functions with requests to the cart.