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

frontend/app/lib/destinations/copy.dart

@@ -0,0 +1,33 @@
+import 'package:sxchnge_wallet/sxchnge_wallet.dart';
+
+import '../generated/i18n/app_localizations.dart';
+
+String destinationType(AppLocalizations l, DestinationType type) =>
+    switch (type) {
+      DestinationType.crypto => l.dCrypto,
+      DestinationType.card => l.dCard,
+      DestinationType.russianBank => l.dBank,
+    };
+String destinationIssue(AppLocalizations l, DestinationIssue issue) =>
+    switch (issue) {
+      DestinationIssue.invalid => l.dInvalid,
+      DestinationIssue.unavailable => l.dTemporary,
+      DestinationIssue.uncertain => l.dUncertain,
+      DestinationIssue.conflict => l.dConflict,
+      DestinationIssue.removed => l.dRemoved,
+      DestinationIssue.expired => l.dCardExpired,
+      DestinationIssue.bankChanged => l.dBankChanged,
+      DestinationIssue.authorization => l.dAuthorization,
+      DestinationIssue.unsupported => l.dUnsupported,
+      DestinationIssue.duplicate => l.dDuplicate,
+      DestinationIssue.replacementRequired => l.dReplacementRequired,
+    };
+String eligibilityText(AppLocalizations l, PayoutEligibility e) =>
+    e.reason != null
+    ? destinationIssue(l, e.reason!)
+    : switch (e.state) {
+        EligibilityState.eligible => l.dEligible,
+        EligibilityState.temporarilyUnavailable => l.dTemporary,
+        EligibilityState.requiresAction => l.dAction,
+        EligibilityState.unsupported => l.dUnsupported,
+      };