The registered backup callback can be reused later when a new backup is started. There is no need to cancel it and register a new callback in such a case.
Restore from backup:
```swift
letresult=trymessenger.restoreBackup(
backupData:...,
backupPassphrase:"backup-passphrase"
)
// handle restore result
```
If no error was thrown during restoration, the `Messenger` is already loaded, started, connected, and logged in.