UnityWebRequest - Set sessionId as a Cookie: Refused to set unsafe header Cookie

Question

I'm facing a problem with setting the sessionId cookie in the UnityWebRequest.

public static class CheckSession_LiveHandler
    {
        public static IEnumerator Send(APIRequest<CheckSession.Request> _request, APIResponse<CheckSession.Result> _onComplete)
        { 

            Debug.Log("CheckSession_LiveHandler: " + _request.request.sessionId);

            string endpoint = EnvironmentSettings.GetVariable<string>("ESCROW_SERVICE_URL");
            
            using (UnityWebRequest request = UnityWebRequest.Get( $"{endpoint}/session"))
            {
                request.SetRequestHeader("Cookie", $"{sessionIdKey}={sessionIdValue}");
                
                yield return request.SendWebRequest();

                var data = request.downloadHandler.text;
                CheckSession.Result result  = JsonConvert.DeserializeObject<CheckSession.Result>(data);

                if (request.isNetworkError || request.isHttpError)
                { 
                    
                   [...]
                }
                else
                {
                   [...]
                }
            }
        }
    }

The error in the browser console is as follows:

Refused to set unsafe header "Cookie"

We need to send the session cookie value to fetch user data related to the session.

The game is running on a WebGL client.

I've tried to modify the fetch function to include "credentials" in the options, but it doesn't work.

Do you know how I can send the cookie in the request?