feat(payment): enhance TwentyCard payment integration and update configuration

- Added support for optional Email and NationalId fields in PaymentRequest for TwentyCard transactions.
- Updated TwentyCardPaymentService to handle multipart/form-data requests and improved error handling.
- Modified appsettings and configuration files for both production and staging environments to include updated BaseUrl and credentials for TwentyCard.
- Updated README to reflect the new documentation location.

src/CMSMicroservice.Infrastructure/Services/Payment/TwentyCardPaymentService.cs

@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.Net.Http;
-using System.Text;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using CMSMicroservice.Application.Common.Interfaces;
@@ -11,7 +10,7 @@ namespace CMSMicroservice.Infrastructure.Services.Payment;
 
 /// <summary>
 /// درگاه پرداخت بیست‌کارت (20Card IPG Merchant API).
-/// مبلغ ورودی به تومان است (مثل بقیهٔ سیستم).
+/// مبلغ ورودی به تومان است. درخواست‌ها به‌صورت multipart/form-data ارسال می‌شوند.
 /// </summary>
 public class TwentyCardPaymentService : IPaymentGatewayService
 {
@@ -55,12 +54,15 @@ public class TwentyCardPaymentService : IPaymentGatewayService
     {
         try
         {
-            var amount = (long)request.Amount;
+            var amount = ((long)request.Amount).ToString();
             var payerName = string.IsNullOrWhiteSpace(request.Name)
                 ? (string.IsNullOrWhiteSpace(request.Mobile) ? "کاربر" : request.Mobile)
                 : request.Name.Trim();
+            var invoice = string.IsNullOrWhiteSpace(request.Invoice)
+                ? request.UserId.ToString()
+                : request.Invoice;
 
-            var body = new Dictionary<string, object?>
+            using var content = BuildForm(new Dictionary<string, string>
             {
                 ["terminal_id"] = _terminalId,
                 ["terminal_username"] = _terminalUsername,
@@ -68,19 +70,19 @@ public class TwentyCardPaymentService : IPaymentGatewayService
                 ["amount"] = amount,
                 ["name"] = payerName,
                 ["mobile"] = request.Mobile ?? string.Empty,
-                ["invoice"] = string.IsNullOrWhiteSpace(request.Invoice)
-                    ? request.UserId.ToString()
-                    : request.Invoice,
+                ["invoice"] = invoice,
                 ["callback"] = request.CallbackUrl,
-                ["description"] = request.Description
-            };
+                ["description"] = request.Description ?? string.Empty
+            });
+
+            if (!string.IsNullOrWhiteSpace(request.Email))
+                content.Add(new StringContent(request.Email), "email");
+            if (!string.IsNullOrWhiteSpace(request.NationalId))
+                content.Add(new StringContent(request.NationalId), "national_id");
 
             _logger.LogInformation(
                 "TwentyCard payment request: Amount={Amount} Toman, User={UserId}, Invoice={Invoice}",
-                amount, request.UserId, body["invoice"]);
-
-            using var content = new StringContent(
-                JsonSerializer.Serialize(body, JsonOptions), Encoding.UTF8, "application/json");
+                amount, request.UserId, invoice);
 
             var response = await _httpClient.PostAsync("api/pgw/merchant/request", content, cancellationToken);
             var responseBody = await response.Content.ReadAsStringAsync(cancellationToken);
@@ -108,7 +110,9 @@ public class TwentyCardPaymentService : IPaymentGatewayService
                 return new PaymentInitiateResult
                 {
                     IsSuccess = false,
-                    ErrorMessage = result?.Message ?? "ایجاد تراکنش ۲۰کارت ناموفق بود"
+                    ErrorMessage = result?.Message
+                        ?? result?.Error?.Message
+                        ?? "ایجاد تراکنش ۲۰کارت ناموفق بود"
                 };
             }
 
@@ -155,17 +159,14 @@ public class TwentyCardPaymentService : IPaymentGatewayService
                 };
             }
 
-            var body = new Dictionary<string, object?>
+            using var content = BuildForm(new Dictionary<string, string>
             {
                 ["terminal_id"] = _terminalId,
                 ["terminal_username"] = _terminalUsername,
                 ["terminal_password"] = _terminalPassword,
                 ["authority"] = refId,
-                ["amount"] = (long)amountInToman
-            };
-
-            using var content = new StringContent(
-                JsonSerializer.Serialize(body, JsonOptions), Encoding.UTF8, "application/json");
+                ["amount"] = ((long)amountInToman).ToString()
+            });
 
             var response = await _httpClient.PostAsync("api/pgw/merchant/verify", content, cancellationToken);
             var responseBody = await response.Content.ReadAsStringAsync(cancellationToken);
@@ -236,10 +237,25 @@ public class TwentyCardPaymentService : IPaymentGatewayService
         });
     }
 
+    private static MultipartFormDataContent BuildForm(Dictionary<string, string> fields)
+    {
+        var form = new MultipartFormDataContent();
+        foreach (var (key, value) in fields)
+            form.Add(new StringContent(value ?? string.Empty), key);
+        return form;
+    }
+
     private sealed class TwentyCardRequestResponse
     {
         public string? Message { get; set; }
         public TwentyCardRequestData? Data { get; set; }
+        public TwentyCardErrorBody? Error { get; set; }
+    }
+
+    private sealed class TwentyCardErrorBody
+    {
+        public string? Code { get; set; }
+        public string? Message { get; set; }
     }
 
     private sealed class TwentyCardRequestData