An error is shown when conditional `OptionConfigurations` attribute of `AWS::RDS::OptionGroup` resource is missing

[Zyava]

cfn-lint version: 0.59.0

cfn-lint produces an error when conditional OptionConfigurations attribute of AWS::RDS::OptionGroup resource is missing

E3003 Property OptionConfigurations missing at Resources/DatabaseOptionGroup/Properties

Description of issue.

For some reason OptionConfigurations conditional attribute in the [AWS::RDS::OptionGroup spec] (https://d3teyb21fexa9r.cloudfront.net/latest/gzip/CloudFormationResourceSpecification.json) is marked as required:

    "AWS::RDS::OptionGroup": {
      "Documentation": "http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-optiongroup.html",
      "Properties": {
...
        "OptionConfigurations": {
          "Documentation": "http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-rds-optiongroup.html#cfn-rds-optiongroup-optionconfigurations",
          "DuplicatesAllowed": true,
          "ItemType": "OptionConfiguration",
          "Required": true,
          "Type": "List",
          "UpdateType": "Immutable"
        },

and cfn-lint still produces an error

E3003 Property OptionConfigurations missing at Resources/DatabaseOptionGroup/Properties

However, both AWS Cloudformation service itself and aws cloudformation validate-template cli command accept template below without any errors.

  DatabaseOptionGroup:
    Type: AWS::RDS::OptionGroup
    Properties:
      EngineName: mysql
      MajorEngineVersion: 8.0
      OptionGroupDescription: Database MySQL
      Tags:
      - Key: generated-by
        Value: cloudformation