Add real-world E2E tests

### Things to check first

- [x] I have searched the existing issues and didn't find my feature already requested there

### Feature description

While the current test coverage is high, the test are mostly generation centric.
Code generation will always be as correct as much the programmer's understanding of SQLAlchemy spec.

However, we are lacking the ability to evaluate the generated code against bonafide databae instances in several simple use cases

### Use case

We are encountering occasional regressions due the lack of such tests