Merge pull request #14021 from Automattic/vkarpov15/gh-14020

docs(migrating_to_7): add note about requiring `new` with `ObjectId`

Author: vkarpov15

docs/migrating_to_7.md

@@ -15,6 +15,7 @@ If you're still on Mongoose 5.x, please read the [Mongoose 5.x to 6.x migration
 * [Removed `remove()`](#removed-remove)
 * [Dropped callback support](#dropped-callback-support)
 * [Removed `update()`](#removed-update)
+* [ObjectId requires `new`](#objectid-requires-new)
 * [Discriminator schemas use base schema options by default](#discriminator-schemas-use-base-schema-options-by-default)
 * [Removed `castForQueryWrapper()`, updated `castForQuery()` signature](#removed-castforquerywrapper)
 * [Copy schema options in `Schema.prototype.add()`](#copy-schema-options-in-schema-prototype-add)
@@ -178,6 +179,23 @@ await Model.updateOne(filter, update);
 await doc.updateOne(update);
 ```
 
+<h2 id="objectid-requires-new"><a href="#objectid-requires-new">ObjectId requires <code>new</code></a></h2>
+
+In Mongoose 6 and older, you could define a new ObjectId without using the `new` keyword:
+
+```javascript
+// Works in Mongoose 6
+// Throws "Class constructor ObjectId cannot be invoked without 'new'" in Mongoose 7
+const oid = mongoose.Types.ObjectId('0'.repeat(24));
+```
+
+In Mongoose 7, `ObjectId` is now a [JavaScript class](https://masteringjs.io/tutorials/fundamentals/class), so you need to use the `new` keyword.
+
+```javascript
+// Works in Mongoose 6 and Mongoose 7
+const oid = new mongoose.Types.ObjectId('0'.repeat(24));
+```
+
 <h2 id="discriminator-schemas-use-base-schema-options-by-default"><a href="#discriminator-schemas-use-base-schema-options-by-default">Discriminator schemas use base schema options by default</a></h2>
 
 When you use `Model.discriminator()`, Mongoose will now use the discriminator base schema's options by default.