I’ve published a set of code-gened API stubs for AWS Cognito: https://package.elm-lang.org/packages/the-sett/elm-aws-cognito/latest/
I am planning on spending some time working with that before publishing any more stubs. I am aiming to create a module around that for user sign-up/sign-in with a more user friendly API.
Other stubs can be generated, though not all services are yet supported. It depends on the protocol the service uses, only JSON is currently supported and there are QUERY, REST_JSON and REST_XML types too.
If you do find yourself wanting a stub generated but the code generator is not up to the job, please raise an issue against it: https://github.com/rupertlssmith/elm-aws-codegen/issues. Thanks.