Port #14415 to 7.x

lib/model.js

@@ -3058,7 +3058,7 @@ Model.startSession = function() {
  * @param {Object} [options] see the [mongodb driver options](https://mongodb.github.io/node-mongodb-native/4.9/classes/Collection.html#insertMany)
  * @param {Boolean} [options.ordered=true] if true, will fail fast on the first error encountered. If false, will insert all the documents it can and report errors later. An `insertMany()` with `ordered = false` is called an "unordered" `insertMany()`.
  * @param {Boolean} [options.rawResult=false] if false, the returned promise resolves to the documents that passed mongoose document validation. If `true`, will return the [raw result from the MongoDB driver](https://mongodb.github.io/node-mongodb-native/4.9/interfaces/InsertManyResult.html) with a `mongoose` property that contains `validationErrors` and `results` if this is an unordered `insertMany`.
- * @param {Boolean} [options.lean=false] if `true`, skips hydrating and validating the documents. This option is useful if you need the extra performance, but Mongoose won't validate the documents before inserting.
+ * @param {Boolean} [options.lean=false] if `true`, skips hydrating the documents. This means Mongoose will **not** cast or validate any of the documents passed to `insertMany()`. This option is useful if you need the extra performance, but comes with data integrity risk. Consider using with [`castObject()`](https://mongoosejs.com/docs/api/model.html#Model.castObject()).
  * @param {Number} [options.limit=null] this limits the number of documents being processed (validation/casting) by mongoose in parallel, this does **NOT** send the documents in batches to MongoDB. Use this option if you're processing a large number of documents and your app is running out of memory.
  * @param {String|Object|Array} [options.populate=null] populates the result documents. This option is a no-op if `rawResult` is set.
  * @param {Boolean} [options.throwOnValidationError=false] If true and `ordered: false`, throw an error if one of the operations failed validation, but all valid operations completed successfully.