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/MyContactFeature/MyContactFeature.swift

@@ -285,6 +285,7 @@ public let myContactReducer = Reducer<MyContactState, MyContactAction, MyContact
         let contactId = try env.messenger.e2e.tryGet().getContact().getId()
         if var dbContact = try env.db().fetchContacts(.init(id: [contactId])).first {
           let facts = try env.messenger.ud.tryGet().getFacts()
+          dbContact.username = facts.get(.username)?.value
           dbContact.email = facts.get(.email)?.value
           dbContact.phone = facts.get(.phone)?.value
           try env.db().saveContact(dbContact)