Add WAFFLE_SWITCH_MODEL to Configuring Waffle page (#535)

* Add `WAFFLE_SWITCH_MODEL` to Configuring Waffle page

Fixes #454

Add `WAFFLE_SWITCH_MODEL` and `WAFFLE_SAMPLE_MODEL` settings to the "Configuring Waffle" documentation page.

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docs/starting/configuring.rst

@@ -28,6 +28,22 @@ behavior.
     Needs to be set at the start of a project, as the Django migrations framework does not
     support changing swappable models after the initial migration.
 
+``WAFFLE_SWITCH_MODEL``
+    The Django model that will be used for switches. Defaults to ``waffle.Switch``, which
+    provides basic switch functionality. This can be swapped for a custom Switch model if
+    additional fields or behaviors are needed. The custom model must inherit from
+    ``waffle.models.AbstractBaseSwitch``. Needs to be set at the start of a project, as
+    Django’s migration framework does not support changing swappable models after the
+    initial migration.
+
+``WAFFLE_SAMPLE_MODEL``
+    The Django model that will be used for samples. Defaults to ``waffle.Sample``, which
+    provides basic sample functionality. This can be swapped for a custom Sample model if
+    additional fields or behaviors are needed. The custom model must inherit from
+    ``waffle.models.AbstractBaseSample``. Needs to be set at the start of a project, as
+    Django’s migration framework does not support changing swappable models after the
+    initial migration.
+
 ``WAFFLE_SWITCH_DEFAULT``
     When a Switch is undefined in the database, Waffle considers it
     ``False``.  Set this to ``True`` to make Waffle consider undefined