This is the tracking ticket to enable a big chunk of the SPM-3541 project. Notably, it introduces a new aggregation stage ($rankFusion) and a new expression ($sigmoid).

See the linked project's design document for more details. This feature flag/milestone notably introduces only a partial $rankFusion stage and the $sigmoid expression. $rankFusion is notably still lacking support for 'scoreDetails', which will be coming in follow-up work (SERVER-94570 and linked tickets). Other follow-up work includes $scoreFusion, $minMaxScalar, and other stuff in that design document.

Description of Linked Ticket

This feature flag does not depend on FCV checks. Nevertheless, we should add a test case like this one: https://github.com/mongodb/mongo/blob/05da13f9ae56d4379c3dd1611743c08c520580f1/jstests/multiVersion/targetedTestsLastLtsFeatures/bindata_convert_numeric_view_upgrade_downgrade.js

Note we combined this ticket with https://jira.mongodb.org/browse/SERVER-98370 - closing that out. It's hard to do them independently.