Return error when paging with cursor method while using sample

[PeterLombaers]

When sampling records from OpenAlex you must use basic paging instead of cursor paging (see the OpenAlex docs).

Currently pyalex has cursor paging as the default method. If you combine sample with paginate it will present the first page and then silently stop paging, without any error. For example, the following test fails:

def test_paging_with_sample():
    p = Authors().sample(26).paginate(per_page=25)
    assert sum(len(page) for page in p) == 26

Pyalex will choose the default cursor method, and only return the first page. So the left side of the assert statement will be 25.

In this pull request I make pyalex raise a ValueError when trying to use cursor pagination with sampling. If you want, I can also change it so that the default method for pagination becomes page in case of sampling, but I thought it was better to be explicit and just let the user know that their combination is not allowed. Let me know if you think differently and I'll update my changes!

[J535D165]

Nice catch!