Add an AWS interface-style endpoint to a VPC (supported by CLI, but not by CF)

I have a VPC that needs an endpoint to connect with kinesis streams. Kinesis streams can only be connected from a VPC using an interface endpoint (not a gateway endpoint).

Cloudformation does not appear to permit interface endpoints to be created. The CLI does, though.

So how do I tell my serverless.yml to create the needed endpoint for the VPC when the VPC is created?

You can add aws resource with cloudformation codes directly into serverless.yml

Sample code for you AWS::EC2::VPCEndpoint