Refactor the use of Namespaces everywhere. #694
Description
To me it makes it much harder to see what information functions expect from their signatures, and at times code has to be carefully analyzed (or checked at runtime) to determine the exact content of arguments. I propose to replace (most) Namespaces by dataclasses or pydantic models, whenever dynamic assignment isn't necessary. Might need to use something like Pydantic's TypedDict to support merging out of the box.