我正在尝试使用Client credential grant（https：//discord.com/developers/docs/topics/oauth2#client-credentials-grant）连接到Discord的开放身份验证端点
Discord要求将scope作为urlencoded字符串发送：identify%20email%20guilds
默认情况下，C# HttpClient似乎将空格转换为+，而不是%20。
以下代码

var scopeasStr = string.Join(" ", opts.Scopes);
            //scopeasStr = HttpUtility.UrlEncode(scopeasStr);
            //scopeasStr = Uri.EscapeDataString(scopeasStr);

            var nvc = new List<KeyValuePair<string, string>>();
            nvc.Add(new KeyValuePair<string, string>("grant_type", opts.GrantType));
            nvc.Add(new KeyValuePair<string, string>("scope", scopeasStr));

            var content = new FormUrlEncodedContent(nvc);
            var requestMessage = new HttpRequestMessage(HttpMethod.Post, $"{apiUrl}/oauth2/token");
            requestMessage.Content = content;

            var response = await externalHttpClient.SendAsync(requestMessage);

生成以下请求

POST https://discord.com/api/v10/oauth2/token HTTP/1.1
Host: discord.com
Authorization: Basic VerySecret
Content-Type: application/x-www-form-urlencoded
Content-Length: 57

grant_type=client_credentials&scope=identify+guilds+email

返回一个400 Bad Request

{"error": "invalid_scope", "error_description": "The requested scope is invalid, unknown, or malformed."}

我试着用scopeasStr = Uri.EscapeDataString(scopeasStr);来编码这个值，但是%20被httpClient编码成了%2520

POST https://discord.com/api/v10/oauth2/token HTTP/1.1
Host: discord.com
Authorization: Basic VerySecret
Content-Type: application/x-www-form-urlencoded
Content-Length: 65

grant_type=client_credentials&scope=identify%2520guilds%2520email

• 当只发送一个作用域时，请求有效。所以肯定是作用域中的空间导致了这个问题。我已经向Discord支持部门确认了他们只接受%20来分隔作用域。
• 我应该如何使用HttpClient正确地对此进行编码？

完整C#代码：

public static async Task Authenticate(this HttpClient client, AuthenticateOptions opts, bool forceNew = false)
        {
            if (client.DefaultRequestHeaders.Authorization == null || forceNew)
            {
                var externalHttpClient = new HttpClient();

                var apiUrl = opts.EndPointUrl;
                var clientId = opts.ClientId;
                var secret = opts.ClientSecret;
                var scopeasStr = string.Join(" ", opts.Scopes);
                //scopeasStr = HttpUtility.UrlEncode(scopeasStr);
                //scopeasStr = Uri.EscapeDataString(scopeasStr);
                externalHttpClient.BaseAddress = new Uri(apiUrl);

                var nvc = new List<KeyValuePair<string, string>>();
                nvc.Add(new KeyValuePair<string, string>("grant_type", opts.GrantType));

                nvc.Add(new KeyValuePair<string, string>("scope", scopeasStr));
                var content = new FormUrlEncodedContent(nvc);
                var requestMessage = new HttpRequestMessage(HttpMethod.Post, $"{apiUrl}/oauth2/token");
                requestMessage.Content = content;
                var authenticationString = $"{clientId}:{secret}";
                var base64EncodedAuthenticationString = Convert.ToBase64String(Encoding.ASCII.GetBytes(authenticationString));
                requestMessage.Headers.Authorization = new AuthenticationHeaderValue("Basic", base64EncodedAuthenticationString);

                var response = await externalHttpClient.SendAsync(requestMessage);
                if (response.IsSuccessStatusCode)
                {
                    var value = await response.ParseResponse();
                    var json = JObject.Parse(value);
                    json.TryGetValue("access_token", out var v);
                    var accessToken = v.Value<string>();
                    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("bearer", accessToken);

                }
                else
                {
                    var value = await response.ParseResponse();
                    Console.Write($"{response.StatusCode} - {value}");
                    Assert.Fail();
                }

            }
        }