getToken method
      
  
Future<AuthToken?> 
getToken(
    
- AuthServer server, {
- String? byAccessToken,
- String? byRefreshToken,
override
    Returns a AuthToken searching by its access token or refresh token.
Exactly one of byAccessToken and byRefreshToken may be non-null, if not, this method must throw an error.
If byAccessToken is not-null and there exists a matching AuthToken.accessToken, return that token.
If byRefreshToken is not-null and there exists a matching AuthToken.refreshToken, return that token.
If no match is found, return null.
server is the AuthServer requesting the AuthToken.
Implementation
@override
Future<AuthToken?> getToken(AuthServer server,
    {String? byAccessToken, String? byRefreshToken}) async {
  if (byAccessToken != null && byRefreshToken != null) {
    throw ArgumentError(
        "Exactly one of 'byAccessToken' or 'byRefreshToken' must be non-null.");
  }
  final query = Query<ManagedAuthToken>(context!);
  if (byAccessToken != null) {
    query.where((o) => o.accessToken).equalTo(byAccessToken);
  } else if (byRefreshToken != null) {
    query.where((o) => o.refreshToken).equalTo(byRefreshToken);
  } else {
    throw ArgumentError(
        "Exactly one of 'byAccessToken' or 'byRefreshToken' must be non-null.");
  }
  final token = await query.fetchOne();
  return token?.asToken();
}