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/ContactFeature/ContactView.swift

@@ -116,6 +116,7 @@ public struct ContactView: View {
           } header: {
             Text("Contact")
           }
+          .textSelection(.enabled)
 
           Section {
             ContactAuthStatusView(dbContact.authStatus)