Restore contacts from backup

XXClient library

• Improve error handling in UdMultiLookupCallback.

xx-messenger example

• Improve backup restoration.
• Restore contacts.
• Add contact lookup feature.
• Display contact ids.
• Improve sending requests.
• Restore username from restored facts, not from restored params.

Examples/xx-messenger/Sources/RestoreFeature/RestoreFeature.swift

@@ -135,7 +135,7 @@ public let restoreReducer = Reducer<RestoreState, RestoreAction, RestoreEnvironm
         let facts = try env.messenger.ud.tryGet().getFacts()
         try env.db().saveContact(Contact(
           id: try env.messenger.e2e.tryGet().getContact().getId(),
-          username: result.restoredParams.username,
+          username: facts.get(.username)?.value,
           email: facts.get(.email)?.value,
           phone: facts.get(.phone)?.value,
           createdAt: env.now()