Mongo-types

Remove `id: Any` from base document, requiring all tables to define their id explicitly.
While being slightly more verbose we get better type checking since `id` will be a
proper type (`str`, `ObjectId`, etc) rather than `Any`.

Fix the `save()` method to return `Self` rather than `Document`

Remove usages of `dataclass` from types and document changes
required for `queryset_manger` behavior replicated with class methods

Initial release