Remediate CDK Warnings

Remediate these warnings (do not ignore)

* installLatestAwsSdk was not specified, and defaults to true. You probably do not want this. Set the global context flag '@aws-cdk/customresources:installLatestAwsSdkDefault' to false to switch this behavior off project-wide, or set the property explicitly to true if you know you need to call APIs that are not in Lambda's built-in SDK version. [ack: @aws-cdk/custom-resources:installLatestAwsSdkNotSpecified]
* AwsSolutions-DDB3: The DynamoDB table does not have Point-in-time Recovery enabled.
* AwsSolutions-EC23: 'AwsSolutions-EC23' threw an error during validation. This is generally caused by a parameter referencing an intrinsic function. You can suppress the "CdkNagValidationFailure" to get rid of this error. For more details enable verbose logging.'