[UsmanGhias]

Summary

On Django 5.1+, index_together was removed from django.db.models.options.DEFAULT_NAMES. Django adapted its own ModelState.render (ticket #34856) to prune index_together before constructing the Meta class, allowing historical migrations containing index_together to render without errors.

In psqlextra, PostgresModelState.render() was constructing Meta directly from **self.options:

meta = type(
    "Meta",
    (),
    {"app_label": self.app_label, "apps": apps, **self.options},
)

When historical migrations for custom or partitioned models still contain index_together in their options, Django 5.1+ throws:

TypeError: 'class Meta' got invalid attribute(s): index_together

Changes

1. In psqlextra/backend/migrations/state/model.py, prune index_together from meta_options prior to calling type("Meta", ...):

   meta_options = {**self.options} if self.options else {}
   meta_options.pop("index_together", None)

2. Added test_partitioned_model_render_index_together in tests/test_partitioned_model_state.py asserting that historical partitioned model state with index_together renders cleanly without raising TypeError.

Closes #286