Add examples/server_datamodel.py to the examples documentation page

[SergioCc13]

While going through the examples I noticed examples/server_datamodel.py is present in the repo and is exercised by CI (test/examples/test_examples.py::test_server_datamodel), but it is not referenced in doc/source/examples.rst, so it does not show up in the published documentation next to the other server_* examples.

I have a small doc-only change ready that adds it to the "Advanced examples" section using the same automodule format as the neighbouring entries. Docs build cleanly locally with sphinx -b html (no new warnings).

Is such a PR welcome, or was this example intentionally kept out of the docs?

[janiversen]

Feel free to submit a PR.