Wrong typing on $mergeObjects with an object

[Naeoth]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

6.8.3

Node.js version

16.15.0

MongoDB server version

5.0

Typescript version (if applicable)

4.9.4

Description

In a $group step of an aggregation with an inner $mergeObjects, the plain object type is missing in ObjectExpression.

Maybe adding { [key: string]: AccumulatorOperator } is the solution?

Steps to Reproduce

import { Schema, model } from "mongoose"

const schema = new Schema({ status: String })
const documentModel = model("Document", schema)

documentModel.aggregate([{
  $group: {
    _id: "$_id",
    merged: {
      $mergeObjects: {
        status: "$status", // typing error here but valid as query
      },
    },
  },
}])

Expected Behavior

No typing error.