link method
Implementation
@override
Future<void> link(AuthCredential credential) async {
final user = auth.currentUser;
if (user != null) {
try {
await user.linkWithCredential(credential);
} on Exception catch (err) {
value = AuthFailed(err);
}
} else {
throw Exception(
"Can't link the credential: no user is currently signed in",
);
}
}