request for contributions: add some end-to-end tests from modern polars

[MarcoGorelli]

In Narwhals we have some end-to-end TPC-H tests, which have been really useful to find some issues not covered by unit tests

Modern Polars is published here: https://kevinheavey.github.io/modern-polars/

it would be good to take some examples from there and make a modern_polars_test file in narwhals which executes some of them and asserts the output matches expected output

if any example from there requires a feature missing from narwhals, please open an issue to discuss it

please make sure that the tests are runnable without large data files - we should be able to generate a small test dataset ourselves or save a small test file in tests/data

[CLWilliam]

Hi there! Looking at working at this one! are you aiming at only trying things out on the smaller datasets as saved on the modern polars small datasets? they're all quite managable size-wise!

[MarcoGorelli]

Hey - yeah small datasets so we can run in ci

[skritsotalakis]

@MarcoGorelli Is this still in scope? I can move it forward right away

[MarcoGorelli]

yup, sure, thanks! #2177 is a good starting point