Support for more general codegen

[banool]

This is more of a question than an issue. In my fork here I have implemented changes that allow me to skip a lot of the codegen.

https://github.com/banool/async-graphql-reverse/

Notably it is possible to opt out of all the scalars stuff, GraphQL stuff, etc. I've added support for having additional attributes added. With all that combined you can generate types that you use with Serde instead of the async-graphql stack.

My suspicion is that this use case is niche enough that it doesn't really belong in your version of the crate, but I want to see what you think.

For now I'll just make of my fork but if you find all the changes there acceptable, I'd love to merge them in.

Thanks!

[tacogips]

@banool At this moment, this tool only includes functionalities to address the needs of my team, and it is likely lacking many other features. Currently, I believe it's fine to continue incorporating new features unless there are significant disruptive changes (given that, for now, users are likely only my team and yourself, so there shouldn't be others facing issues:). So Your PR is very welcome!

If the user base grows in the future and conflicts or similar issues arise with functionalities, it might be necessary to perform version updates that break backward compatibility in order to streamline those, but I consider this an inevitable step.