Use newer version of `cattrs`

[rschwanhold]

• Update to 1.8.0 (or newer)
• There might be an error such as cattr.errors.StructureHandlerNotFoundError: Unsupported type: typing.Union[int, wkcuber.mag.Mag]. Register a structure hook for it
• The hooks might be simplified:
  • Instead of this loop, you could register (un-)structuring factories:

  def snake_to_camel_case_overrides(attrs_type):
    return {
        a.name: override(omit_if_default=True, rename=_snake_to_camel_case(a.name))
        for a in attr.fields(attrs_type)
    }
  
  register_unstructure_hook_factory(attrs.has, lambda attrs_type: make_dict_unstructure_fn(cls, dataset_converter,  **snake_to_camel_case_overrides(attrs_type)))
  # same for structuring