AWS::CodeDeploy::BlueGreen - AWS::CodeDeployBlueGreen Transform (CodeDeploy)

Following the instructions [here](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/blue-green.html). I'm getting the following error when trying to update the task definition with a new image.

```
Error: Failed to create ChangeSet cdk-deploy-change-set on MyStack: FAILED, Transform AWS::CodeDeployBlueGreen failed with: Failed to transform template. Failed to parse the "Hooks" section for the provided template. Please ensure the AWS::CodeDeploy::BlueGreen Hook matches the expected schema.
```

Here's the hook
```yml
Transform: AWS::CodeDeployBlueGreen
Hooks:
CodeDeployBlueGreenHook:
Type: AWS::CodeDeploy::BlueGreen
Properties:
ServiceRole: MyRole
Applications:
- Target:
Type: AWS::ECS::Service
LogicalID: ECSService
ECSAttributes:
TaskDefinitions:
- TaskDefBlue
- TaskDefGreen
TaskSets:
- TaskSetBlue
- TaskSetGreen
TrafficRouting:
ProdTrafficRoute:
Type: AWS::ElasticLoadBalancingV2::Listener
LogicalID: LoadBalancer
TestTrafficRoute:
Type: AWS::ElasticLoadBalancingV2::Listener
LogicalID: LoadBalancerTest
TargetGroups:
- BlueTg
- GreenTg
TrafficRoutingConfig:
Type: TimeBasedCanary
TimeBasedCanary:
StepPercentage: 20
BakeTimeMins: 15
AdditionalOptions:
TerminationWaitTimeInMinutes: 30
```

Can your team maybe open source the CodeDeployBlueGreen transform so we can do our own debugging? Otherwise, we'll probably need a little more than "Please ensure the AWS::CodeDeploy::BlueGreen Hook matches the expected schema"—especially given this is a CDK generated schema and it passes all other checks.

Thanks!

cc @clareliguori

Start with the AWS CloudFormation blue-green deployment documentation and the reported AWS::CodeDeployBlueGreen Hook template, then reproduce the ChangeSet failure while updating the ECS task definition image. Determine whether the hook matches the documented schema and whether the transform exposes enough information to identify the rejected field; done means a confirmed cause with an actionable diagnostic or documented correction.

Written by the indexing model from the issue text.