Create new internal Go lib

[svix-mman]

Create new Go internal API client

This client only has the limited set of operations needed for the terraform plugin

note: This is branched from #1884, I will rebase on main once #1884 is merged

[svix-jplatte]

Why add this to the SDK, rather than the terraform package?

[svix-mman]

Why add this to the SDK, rather than the terraform package?

I kinda want to dog food the SDK, it feels bad to generate an extra lib.
Is there any downside to create this internal api?

[svix-jplatte]

I was talking about only generating code there for the internal stuff. I don't see a big downside to this approach, one thing is that it doesn't allow us to later remove the hidden stuff from this repo, but that doesn't seem so important.

[svix-jplatte]

I guess the other approach might be too much extra work 🤷

[svix-mman]

I was talking about only generating code there for the internal stuff. I don't see a big downside to this approach, one thing is that it doesn't allow us to later remove the hidden stuff from this repo, but that doesn't seem so important.

I don't like the idea of exposing the internal workings (executeRequest, etc...) of the SDK publicly

[svix-jplatte]

Don't need to do that, could just duplicate.

The base branch was changed.