Description

Adds the $subtype aggregation expression operator introduced in MongoDB 8.3 (SERVER-103893).

The operator is added to expression-operators.ts with:

• meta: 'expr:type' — same category as $type, which also introspects value types
• version: '8.3.0'
• Alphabetical position between $subtract and $switch

Open Questions

None.

Checklist

• I have signed the Contributor License Agreement (https://www.mongodb.com/legal/contributor-agreement)
• New tests and/or benchmarks are included
• Documentation is changed or added