HasMetadata doesn't work in some subclasses

[wRAR]

This fails:

def test_metadata_with_returns():
    class MyProduct(Product):
        pass

    class CustomProductPage(ProductPage, Returns[MyProduct]):
        pass

    url = ResponseUrl("https://example.com")
    html = b""
    page = CustomProductPage(response=HttpResponse(url=url, body=html))
    metadata = page.metadata

    @field
    def metadata(self) -> MetadataT:
>       value = self.metadata_cls()
E       TypeError: 'NoneType' object is not callable

zyte_common_items/pages.py:67: TypeError

zyte_common_items.pages._get_metadata_class in the case of this CustomProductPage cannot find any HasMetadata base and returns None.

[wRAR]

AFAICS __orig_bases__ is not recursive, so _get_metadata_class needs to be recursive?