Azure Developer Portal Delegation Signin Issue

Question

I am using developer portal and i want to delegate the signin process from other application. i have this code for signin but it is giving unauthorize error. i have taken this from sample and now trying to login to developer portal with this.

I have checked azure api documentation its the same api there still ""users/" + User.Identity.GetName() + "/token?" return unauthorize

         //create user in APIM as well
                        using (var client = new HttpClient())
                        {
                            client.BaseAddress = new Uri(ApimRestHost);
                            client.DefaultRequestHeaders.Add("Authorization", ApimRestAuthHeader());

                            var ApimUser = new
                            {
                                keyType = "primary",
                                expiry = ApimRestExpiry
                            };

                            var ApimUserJson = JsonSerializer.Serialize(ApimUser);

                            HttpResponseMessage response = await client.PostAsync("users/" + User.Identity.GetName() + "/token?api-version=2023-03-01-preview", this.GetContent(ApimUserJson));
                            if (response.IsSuccessStatusCode)
                            {
                                //We got an SSO token - redirect
                                HttpContent receiveStream = response.Content;
                                var SsoUrlJson = await receiveStream.ReadAsStringAsync();
                                var su = JsonSerializer.Deserialize<SsoUrl>(SsoUrlJson);

                                //We need to encode the primary key before passing it to the sso url.
                                string url = string.Format("{0}/signin-sso?token={1}", developerPortalUrl, HttpUtility.UrlEncode(su.value));
                                return Redirect(url);
                            }
                            else
                            {
                                @ViewBag.Message = "APIM REST Connection Error: " + response.StatusCode;
                                return View();
                            }
                        }

// token for headers
public string ApimRestAuthHeader()
        {
            using (var encoder = new HMACSHA512(Encoding.UTF8.GetBytes(ApimRestPK)))
            {
                var dataToSign = ApimRestId + "\n" + ApimRestExpiry.ToString("O", CultureInfo.InvariantCulture);
                var hash = encoder.ComputeHash(Encoding.UTF8.GetBytes(dataToSign));
                var signature = Convert.ToBase64String(hash);
                var encodedToken = string.Format("SharedAccessSignature uid={0}&ex={1:o}&sn={2}", ApimRestId, ApimRestExpiry, signature);
                return encodedToken;
            }
        }

i have tried multiple token i have delegation token now what should i change for authorization of that api