Update release notes

docs/topics/3.0-announcement.md

@@ -664,14 +664,26 @@ The `COMPACT_JSON` setting has been added, and can be used to revert this behavi
 
 #### File fields as URLs
 
-The `FileField` and `ImageField` classes are now represented as URLs by default. You should ensure you set Django's standard `MEDIA_URL` setting appropriately.
+The `FileField` and `ImageField` classes are now represented as URLs by default. You should ensure you set Django's [standard `MEDIA_URL` setting](https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-MEDIA_URL) appropriately, and ensure your application [serves the uploaded files](https://docs.djangoproject.com/en/dev/howto/static-files/#serving-uploaded-files-in-development).
 
-You can revert this behavior, and display filenames as the representation, using the `UPLOADED_FILES_USE_URL` settings key:
+You can revert this behavior, and display filenames in the representation by using the `UPLOADED_FILES_USE_URL` settings key:
 
     REST_FRAMEWORK = {
         'UPLOADED_FILES_USE_URL': False
     }
 
+You can also modify serializer fields individually, using the `use_url` argument:
+
+    uploaded_file = serializers.FileField(user_url=False)
+
+Also note that you should pass the `request` object to the serializer as context when instantiating it, so that a fully qualified URL can be returned. Returned URLs will then be of the form `https://example.com/url_path/filename.txt`. For example:
+
+    context = {'request': request}
+    serializer = ExampleSerializer(instance, context=context)
+    return Response(serializer.data)
+
+If the request is omitted from the context, the returned URLs will be of the form `/url_path/filename.txt`.
+
 #### Throttle headers using `Retry-After`.
 
 The custom `X-Throttle-Wait-Second` header has now been dropped in favor of the standard `Retry-After` header. You can revert this behavior if needed by writing a custom exception handler for your application.