Closes #9075: Introduce AbortRequest exception for cleanly interrupting object mutations

docs/plugins/development/exceptions.md

@@ -0,0 +1,28 @@
+# Exceptions
+
+The exception classes listed here may be raised by a plugin to alter NetBox's default behavior in various scenarios.
+
+## `AbortRequest`
+
+NetBox provides several [generic views](./views.md) and [REST API viewsets](./rest-api.md) which facilitate the creation, modification, and deletion of objects, either individually or in bulk. Under certain conditions, it may be desirable for a plugin to interrupt these actions and cleanly abort the request, reporting an error message to the end user or API consumer.
+
+For example, a plugin may prohibit the creation of a site with a prohibited name by connecting a receiver to Django's `pre_save` signal for the Site model:
+
+```python
+from django.db.models.signals import pre_save
+from django.dispatch import receiver
+from dcim.models import Site
+from utilities.exceptions import AbortRequest
+
+PROHIBITED_NAMES = ('foo', 'bar', 'baz')
+
+@receiver(pre_save, sender=Site)
+def test_abort_request(instance, **kwargs):
+    if instance.name.lower() in PROHIBITED_NAMES:
+        raise AbortRequest(f"Site name can't be {instance.name}!")
+```
+
+An error message must be supplied when raising `AbortRequest`. This will be conveyed to the user and should clearly explain the reason for which the request was aborted, as well as any potential remedy.
+
+!!! tip "Consider custom validation rules"
+    This exception is intended to be used for handling complex evaluation logic and should be used sparingly. For simple object validation (such as the contrived example above), consider using [custom validation rules](../../customization/custom-validation.md) instead.