CAKE-20 | updated exchange and exchange template pages; created exchange_view_model and applied to exchange and exchange template pages; applied new design to menu widget; changed text validator and amount validator

lib/core/amount_validator.dart

@@ -3,10 +3,11 @@ import 'package:cake_wallet/generated/i18n.dart';
 import 'package:cake_wallet/src/domain/common/wallet_type.dart';
 
 class AmountValidator extends TextValidator {
-  AmountValidator({WalletType type})
+  AmountValidator({WalletType type, bool isAutovalidate = false})
       : super(
             errorMessage: S.current.error_text_amount,
             pattern: _pattern(type),
+            isAutovalidate: isAutovalidate,
             minLength: 0,
             maxLength: 0);
 

lib/core/validator.dart

@@ -16,18 +16,20 @@ class TextValidator extends Validator<String> {
       this.maxLength,
       this.pattern,
       this.length,
+      this.isAutovalidate = false,
       String errorMessage})
       : super(errorMessage: errorMessage);
 
   final int minLength;
   final int maxLength;
   final List<int> length;
+  final bool isAutovalidate;
   String pattern;
 
   @override
   bool isValid(String value) {
     if (value == null || value.isEmpty) {
-      return false;
+      return isAutovalidate ? true : false;
     }
 
     return value.length > (minLength ?? 0) &&