smithy-aws-cloudformation-traits does not set additionalProperties: false on all object types

[workeitel]

CloudFormation requires additionalProperties to be false aws-cloudformation/cloudformation-resource-schema#49

Smithy already applies additionalProperties to the top-level: https://github.com/awslabs/smithy/blob/main/smithy-aws-cloudformation/src/main/java/software/amazon/smithy/aws/cloudformation/schema/fromsmithy/CfnConverter.java#L127-L129

But it needs to be added to every object. Expected output:

"Context": {
    "additionalProperties": false,
    "type": "object",
   ...

[kstich]

Thanks for the report. We'll add an internal JsonSchemaMapper that sets this property by default.