Messed up the base branch/merge - fix (#3065)

docs/eloquent-models/model-class.txt

@@ -30,7 +30,10 @@ to {+odm-short+} models:
 - :ref:`laravel-model-define` demonstrates how to create a model class.
 - :ref:`laravel-authenticatable-model` shows how to set MongoDB as the
   authentication user provider.
-- :ref:`laravel-model-customize` explains several model class customizations.
+- :ref:`laravel-model-customize` explains several model class
+  customizations.
+- :ref:`laravel-third-party-model` explains how to make third-party
+  model classes compatible with MongoDB.
 - :ref:`laravel-model-pruning` shows how to periodically remove models that
   you no longer need.
 - :ref:`laravel-schema-versioning` shows how to implement model schema
@@ -180,7 +183,7 @@ in the Laravel docs.
 .. _laravel-model-cast-data-types:
 
 Cast Data Types
----------------
+~~~~~~~~~~~~~~~
 
 Eloquent lets you convert model attribute data types before storing or
 retrieving data by using a casting helper. This helper is a convenient
@@ -281,6 +284,45 @@ To learn how to change the behavior when attempting to fill a field omitted
 from the ``$fillable`` array, see `Mass Assignment Exceptions <https://laravel.com/docs/{+laravel-docs-version+}/eloquent#mass-assignment-exceptions>`__
 in the Laravel docs.
 
+.. _laravel-third-party-model:
+
+Extend Third-Party Model Classes
+--------------------------------
+
+You can use {+odm-short+} to extend a third-party model class by
+including the ``DocumentModel`` trait when defining your model class. By
+including this trait, you can make the third-party class compatible with
+MongoDB.
+
+When you apply the ``DocumentModel`` trait to a model class, you must
+declare the following properties in your class:
+
+- ``$primaryKey = '_id'``, because the ``_id`` field uniquely
+  identifies MongoDB documents
+- ``$keyType = 'string'``, because {+odm-short+} casts MongoDB
+  ``ObjectId`` values to type ``string``
+
+Extended Class Example
+~~~~~~~~~~~~~~~~~~~~~~
+
+This example creates a ``Planet`` model class that extends the
+``CelestialBody`` class from a package called ``ThirdPartyPackage``. The
+``Post`` class includes the ``DocumentModel`` trait and defines
+properties including ``$primaryKey`` and ``$keyType``:
+
+.. literalinclude:: /includes/eloquent-models/PlanetThirdParty.php
+   :language: php
+   :emphasize-lines: 10,13-14
+   :dedent:
+
+After defining your class, you can perform MongoDB operations as usual.
+
+.. tip::
+
+   To view another example that uses the ``DocumentModel`` trait, see
+   the :ref:`laravel-user-auth-sanctum` section of the User
+   Authentication guide.
+
 .. _laravel-model-pruning:
 
 Specify Pruning Behavior

docs/includes/eloquent-models/PlanetThirdParty.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace App\Models;
+
+use MongoDB\Laravel\Eloquent\DocumentModel;
+use ThirdPartyPackage\CelestialBody;
+
+class Planet extends CelestialBody
+{
+    use DocumentModel;
+
+    protected $fillable = ['name', 'diameter'];
+    protected $primaryKey = '_id';
+    protected $keyType = 'string';
+}

docs/user-authentication.txt

@@ -149,6 +149,11 @@ service providers. To learn more, see `Overriding Default Models
 <https://laravel.com/docs/{+laravel-docs-version+}/sanctum#overriding-default-models>`__
 in the Laravel Sanctum guide.
 
+.. tip::
+
+   To learn more about the ``DocumentModel`` trait, see
+   :ref:`laravel-third-party-model` in the Eloquent Model Class guide.
+
 .. _laravel-user-auth-reminders:
 
 Password Reminders