storeToken method
Implementation
Future<void> storeToken(String userId, String token, {int? expiresIn}) async {
final expiry = expiresIn != null
? DateTime.now().add(Duration(seconds: expiresIn))
: getTokenExpiration(token) ?? DateTime.now().add(Duration(hours: 1));
_tokens[userId] = _TokenInfo(token: token, expirationTime: expiry);
}