logout method

Implementation

@override
Future<bool> logout() async {
  debugPrint('Logging out from Dropbox.');
  if (_isAuthenticated && _token != null) {
    try {
      // Attempt to revoke the token on Dropbox's servers.
      await _dio.post('https://api.dropboxapi.com/2/auth/token/revoke');
      debugPrint('Successfully revoked Dropbox token via API.');
    } catch (e) {
      debugPrint(
          'Failed to revoke Dropbox token via API, but logging out locally anyway.');
    }
  }
  // Clear local state regardless of API call success.
  await _clearToken();
  _token = null;
  _account = null;
  _isAuthenticated = false;
  return true;
}