where filter: make filterting connections possible

(Sorry for the feature request spam, I'm currently evaluating if caisy could be the right thing for a new project)

I would like to create a GraqhQL query with some where: rules, that filter connection items. Meaning that, "give me all posts where the field `categories` includes the category with the field `slug` = `example`"

So for example:

query {
  allPost(where: {category: { slug: { eq: "example" } } }) {
    ...
  }
}