refactor exchange exception

lib/exceptions/exchange/exchange_exception.dart

@@ -0,0 +1,13 @@
+import 'package:stackwallet/exceptions/sw_exception.dart';
+
+enum ExchangeExceptionType { generic, serializeResponseError }
+
+class ExchangeException extends SWException {
+  ExchangeExceptionType type;
+  ExchangeException(super.message, this.type);
+
+  @override
+  String toString() {
+    return message;
+  }
+}

lib/exceptions/exchange/majestic_bank/mb_exception.dart

@@ -0,0 +1,5 @@
+import 'package:stackwallet/exceptions/exchange/exchange_exception.dart';
+
+class MBException extends ExchangeException {
+  MBException(super.message, super.type);
+}

lib/services/exchange/change_now/change_now_api.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:decimal/decimal.dart';
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
+import 'package:stackwallet/exceptions/exchange/exchange_exception.dart';
 import 'package:stackwallet/external_api_keys.dart';
 import 'package:stackwallet/models/exchange/change_now/cn_exchange_estimate.dart';
 import 'package:stackwallet/models/exchange/change_now/estimated_exchange_amount.dart';

lib/services/exchange/exchange_data_loading_service.dart

@@ -55,7 +55,7 @@ class ExchangeDataLoadingService {
       }
     } else {
       Logging.instance.log(
-          "Failed to load changeNOW fixed rate markets: ${response3.exception?.errorMessage}",
+          "Failed to load changeNOW fixed rate markets: ${response3.exception?.message}",
           level: LogLevel.Error);
 
       ref.read(changeNowFixedInitialLoadStatusStateProvider.state).state =
@@ -122,7 +122,7 @@ class ExchangeDataLoadingService {
         }
       } else {
         Logging.instance.log(
-            "Failed to load changeNOW available floating rate pairs: ${response2.exception?.errorMessage}",
+            "Failed to load changeNOW available floating rate pairs: ${response2.exception?.message}",
             level: LogLevel.Error);
         ref.read(changeNowEstimatedInitialLoadStatusStateProvider.state).state =
             ChangeNowLoadStatus.failed;
@@ -130,7 +130,7 @@ class ExchangeDataLoadingService {
       }
     } else {
       Logging.instance.log(
-          "Failed to load changeNOW currencies: ${response.exception?.errorMessage}",
+          "Failed to load changeNOW currencies: ${response.exception?.message}",
           level: LogLevel.Error);
       await Future<void>.delayed(const Duration(seconds: 3));
       ref.read(changeNowEstimatedInitialLoadStatusStateProvider.state).state =

lib/services/exchange/exchange_response.dart

@@ -1,15 +1,4 @@
-enum ExchangeExceptionType { generic, serializeResponseError }
+import 'package:stackwallet/exceptions/exchange/exchange_exception.dart';
-
-class ExchangeException implements Exception {
-  String errorMessage;
-  ExchangeExceptionType type;
-  ExchangeException(this.errorMessage, this.type);
-
-  @override
-  String toString() {
-    return errorMessage;
-  }
-}
 
 class ExchangeResponse<T> {
   late final T? value;

lib/services/exchange/majestic_bank/majestic_bank_api.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 
 import 'package:decimal/decimal.dart';
 import 'package:http/http.dart' as http;
+import 'package:stackwallet/exceptions/exchange/exchange_exception.dart';
 import 'package:stackwallet/models/exchange/majestic_bank/mb_limit.dart';
 import 'package:stackwallet/models/exchange/majestic_bank/mb_order.dart';
 import 'package:stackwallet/models/exchange/majestic_bank/mb_order_calculation.dart';

lib/services/exchange/simpleswap/simpleswap_api.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:decimal/decimal.dart';
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
+import 'package:stackwallet/exceptions/exchange/exchange_exception.dart';
 import 'package:stackwallet/external_api_keys.dart';
 import 'package:stackwallet/models/exchange/response_objects/fixed_rate_market.dart';
 import 'package:stackwallet/models/exchange/response_objects/pair.dart';