WIP: feat: add types for the open API spec methods

[lukasholzer]

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Summary

Fixes #5307

I've taken a look at the ecosystem. There are some libraries that are responsible for generating OpenAPI types but sadly, they are not compatible with how we built and designed our API. If we want to make this a nonbreaking change without having the users update all usages, we have to write our own generation, sadly.

As we have a unique way of how parameters are converted into function parameters, this is crucial. IMHO, we should aim NOT to break the API surface as this library is so widely used in all places.

Therefore I've started writing our custom implementation for it. It's still super WIP.

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