validate method
      
  
ValidationResult
validate(
    
    
- covariant ValidationRequest<String> request,
- covariant String? data
override
    Implementation
@override
ValidationResult validate(
    covariant ValidationRequest<String> request, covariant String? data) {
  if (data == null || request.validationData == null) {
    return ValidationResult.not();
  }
  if (data != request.validationData) {
    return ValidationResult.not();
  } else {
    return ValidationResult.ok(
        // contentType: validationResponse.contentType,
        headers: {
          HttpHeaders.etagHeader: data,
          HttpHeaders.contentLengthHeader: 0
        }, statusCode: 304);
  }
  //
  // if (request.validationData == validationResponse.value) {
  //   return ValidationResult.ok(headers: {
  //     HttpHeaders.etagHeader: validationResponse.value,
  //     HttpHeaders.contentLengthHeader: 0
  //   }, statusCode: 304);
  // } else {
  //   return ValidationResult.not();
  // }
}