Client Certification at API level is not supported

[bigzidane]

Currently it appears we have no way to attach ClientCertification to an API using SAM.

In native CloudFormation, we can use AWS::ApiGateway::Stage resource type and use ClientCertificateId property. However, since we are using AWS::Serverless::Api and this creates AWS::ApiGateway::Stage, it will be difficult to use ClientCertificateId property.

Please advice if we have any way we can implement this one.

[PeterBengtson]

It very much seems that you'll have to use a custom resource for adding/removing a client certificate. This of course always works, but it's wordy and kludgy and a royal pain. Nothing seems to have happened here for over two years.