feat: add interface for new atSign management utilities

packages/dart/npt_flutter/lib/features/onboarding/util/atsign_manager.dart

@@ -0,0 +1,30 @@
+abstract class AtsignInformation {
+  String get atSign;
+  String get rootDomain;
+}
+
+// This will return a map which looks like:
+//
+// {
+//   "@alice": AtsignInformation{ atSign: "@alice", rootDomain: "root.atsign.org" },
+//   "@bob": AtsignInformation{ atSign: "@alice", rootDomain: "vip.ve.atsign.zone" },
+// }
+//
+// Note: AtsignInformation is a class, so usage will look like
+//
+// var atSign = "@alice";
+// var atSignInfo = await getAtsignEntries();
+// var rootDomain = atSignInfo[atSign].rootDomain;
+//
+// Now you have the rootDomain for the existing atSign and can use it to onboard
+// correctly
+
+Future<Map<String, AtsignInformation>> getAtsignEntries() {
+  return Future.value({});
+}
+
+// This class will allow you to store atSign information
+// you need to call this after onboarding a NEW atSign
+Future<bool> saveAtsignInformation(AtsignInformation info) {
+  return Future.value(true);
+}

packages/dart/npt_flutter/lib/features/onboarding/util/pre_offboard.dart

@@ -0,0 +1,8 @@
+// Hand this method the atSign you wish to offboard
+// Returns: a boolean, true = success, false = failed
+Future<bool> preSignout(String atSign) async {
+  // We need to do the following before "signing out"
+  // - Wipe all application state
+  // - Remove the tray icon
+  return true;
+}