Add saved payout destination UX and service contracts (#54)

frontend/packages/sxchnge_wallet/lib/src/transport/wallet.dart

@@ -1,3 +1,4 @@
+import '../destinations/transport.dart';
 import '../models/wallet.dart';
 
 class AccountDTO {
@@ -23,11 +24,13 @@ class RequestDTO {
     this.source,
     this.destination,
     this.amount,
-    this.recipient,
-  );
+    this.recipient, {
+    this.payoutInput,
+  });
   final String kind, source, recipient;
   final String? destination;
   final int amount;
+  final DestinationInputDTO? payoutInput;
 }
 
 class QuoteDTO {
@@ -39,12 +42,16 @@ class QuoteDTO {
     this.credit,
     this.expires,
     this.numerator,
-    this.denominator,
-  );
+    this.denominator, {
+    this.payoutSnapshot,
+    this.payoutTerms,
+  });
   final String id;
   final RequestDTO request;
   final int fee, debit, credit, numerator, denominator;
   final DateTime expires;
+  final DestinationDTO? payoutSnapshot;
+  final PayoutTermsDTO? payoutTerms;
 }
 
 class OperationDTO {
@@ -78,14 +85,28 @@ abstract final class WalletMapper {
     payoutLabel: d.payoutLabel,
     canFund: d.canFund,
   );
-  static RequestDTO request(TransferRequest r) =>
-      RequestDTO(r.kind.name, r.source, r.destination, r.amount, r.recipient);
+  static RequestDTO request(
+    TransferRequest r, {
+    bool includePayoutInput = true,
+  }) => RequestDTO(
+    r.kind.name,
+    r.source,
+    r.destination,
+    r.amount,
+    r.recipient,
+    payoutInput: !includePayoutInput || r.payoutDestination == null
+        ? null
+        : DestinationInputMapper.toDTO(r.payoutDestination!),
+  );
   static TransferRequest fromRequest(RequestDTO d) => TransferRequest(
     kind: TransferKind.values.byName(d.kind),
     source: d.source,
     destination: d.destination,
     amount: d.amount,
     recipient: d.recipient,
+    payoutDestination: d.payoutInput == null
+        ? null
+        : DestinationInputMapper.fromDTO(d.payoutInput!),
   );
   static Quote quote(QuoteDTO d) => Quote(
     id: d.id,
@@ -96,6 +117,17 @@ abstract final class WalletMapper {
     expiresAt: d.expires,
     rateNumerator: d.numerator,
     rateDenominator: d.denominator,
+    payoutTerms: d.payoutTerms == null
+        ? null
+        : PayoutTerms(
+            d.payoutTerms!.amount,
+            d.payoutTerms!.precision,
+            d.payoutTerms!.assetLabel,
+            d.payoutTerms!.expectedSeconds,
+          ),
+    payoutSnapshot: d.payoutSnapshot == null
+        ? null
+        : DestinationMapper.fromDTO(d.payoutSnapshot!),
   );
   static WalletOperation operation(OperationDTO d) => WalletOperation(
     id: d.id,
@@ -105,3 +137,14 @@ abstract final class WalletMapper {
   );
   static AccountProfile profile(ProfileDTO dto) => AccountProfile(dto.locale);
 }
+
+class PayoutTermsDTO {
+  const PayoutTermsDTO(
+    this.amount,
+    this.precision,
+    this.assetLabel,
+    this.expectedSeconds,
+  );
+  final int amount, precision, expectedSeconds;
+  final String assetLabel;
+}