Messenger - restore from backup

XXMessengerClient

• Add MessengerRestoreBackup function wrapper
  • Restore CMix and UserDiscovery from backup
  • Return restored params and contacts
• Add MessengerIsListeningForMessages function

xx-messenger example

• Restore backup from file
• Refactor app startup

Sources/XXMessengerClient/Utils/BackupParams.swift

 import Foundation
 
-public struct BackupParams: Codable {
+public struct BackupParams: Equatable, Codable {
   public init(
     username: String,
     email: String?,