atsign property
Onboards the given atsign if not null. if atsign is null then takes the atsign from keychain. ifatsign is empty then it directly jumps into authenticate without performing onboarding. (or) if atsign is empty then it just presents pairAtSign screen without onboarding the atsign. (or) Just provide an empty string for ignoring existing atsign in keychain or app's atsign.
Implementation
final String? atsign;