Show accepted signup delivery without a second send step (#62)

frontend/packages/sxchnge_auth/lib/src/models/verification.dart

@@ -11,6 +11,13 @@ enum VerificationStatus {
 
 enum VerificationError { expired, invalid, internal, needsAssistance }
 
+/// An accepted email-queue operation, not proof of inbox delivery or activation.
+class VerificationDelivery {
+  const VerificationDelivery({required this.email, required this.isSimulated});
+  final String email;
+  final bool isSimulated;
+}
+
 class VerificationException implements Exception {
   const VerificationException(this.code);
   final VerificationError code;