CW-148 cake pay partial redemptions (#490)

* Ionia custom redemption screen

* update ionia gift card remaining amount with custom value

* [NO-TASK] Fix issues with custom redeem

* replace redeem

* update remaining amount

* fixed from code review

* Add localization

lib/view_model/ionia/ionia_custom_redeem_view_model.dart

@@ -0,0 +1,27 @@
+import 'package:cake_wallet/ionia/ionia_gift_card.dart';
+import 'package:mobx/mobx.dart';
+part 'ionia_custom_redeem_view_model.g.dart';
+class IoniaCustomRedeemViewModel = IoniaCustomRedeemViewModelBase with _$IoniaCustomRedeemViewModel;
+
+abstract class IoniaCustomRedeemViewModelBase with Store {
+  IoniaCustomRedeemViewModelBase(this.giftCard){
+    amount = 0;
+  }
+
+  final IoniaGiftCard giftCard;
+
+  @observable
+  double amount;
+
+  @computed
+  double get remaining =>  amount <= giftCard.remainingAmount ? giftCard.remainingAmount  - amount : 0;
+
+  @computed
+  bool get disableRedeem => amount > giftCard.remainingAmount;
+
+  @action
+  void updateAmount(String text){
+      amount = text.isEmpty ? 0 : (double.parse(text.replaceAll(',', '.')) ?? 0);
+  }
+
+}

lib/view_model/ionia/ionia_gift_card_details_view_model.dart

@@ -12,6 +12,7 @@ abstract class IoniaGiftCardDetailsViewModelBase with Store {
 
   IoniaGiftCardDetailsViewModelBase({this.ioniaService, this.giftCard}) {
     redeemState = InitialExecutionState();
+    remainingAmount = giftCard.remainingAmount;
   }
 
   final IoniaService ioniaService;
@@ -20,11 +21,15 @@ abstract class IoniaGiftCardDetailsViewModelBase with Store {
   @observable
   IoniaGiftCard giftCard;
 
+  @observable
+  double remainingAmount;
+
   @observable
   ExecutionState redeemState;
 
   @action
   Future<void> redeem() async {
+    giftCard.remainingAmount = remainingAmount;
     try {
       redeemState = IsExecutingState();
       await ioniaService.redeem(giftCard);
@@ -35,6 +40,11 @@ abstract class IoniaGiftCardDetailsViewModelBase with Store {
     }
   }
 
+  @action
+  void updateRemaining(double amount){
+    remainingAmount = amount;
+  }
+
   void increaseBrightness() async {
     brightness = await DeviceDisplayBrightness.getBrightness();
     await DeviceDisplayBrightness.setBrightness(1.0);