GroupBy Sorting Behavior with Multiple Sort Fields

Description

When using group_by with multiple sort fields, where one field is _group_found, the secondary sort field appears to be ignored in the results.

Steps to Reproduce

The scenario involves products with multiple offers per product. The index "offers" is denormalized, with each offer containing the associated product data as additional fields.

When you:

1. Group by product_id
2. Sort by _group_found (to prioritize products with the most offers)
   The initial sorting works as expected.

Expected Behavior

Adding a second sort field price:asc with group_limit: 1 should return the lowest-priced offer for each product, while maintaining the primary sort by number of offers per product.

Actual Behavior

Using the sort configuration:

sort_by: '_group_found:desc, price:asc'

The results appear to only respect the _group_found sort order, while ignoring the secondary price sort field.

No source files or tests are named. Start by reproducing the described grouped query against the denormalized "offers" index, using product_id, _group_found:desc, price:asc, and group_limit:1; done means the lowest-priced offer is selected for each product while _group_found remains the primary order.