saveRefreshToken method
Saves the refresh token to secure storage.
Throws a TokenManagerException if an error occurs during saving.
Implementation
@override
Future<void> saveRefreshToken(String token) async {
try {
await _storage.write(key: 'refresh_token', value: token);
} catch (e) {
throw TokenManagerException(TokenErrorMessages.failedToSaveRefreshToken);
}
}