And for now treat partial fetches as a success, since for all
current users partial collection data is better than no data at all.
If an error occurred while fetching a page, this previously
returned a bogus {:ok, {:error, _}} success, causing the error
to be attached to the object as an reply list subsequently
leading to the whole post getting rejected during validation.
Also the pinned collection caller did not actually handle
the preexisting error case resulting in process crashes.
