Increase DATA_UPLOAD_MAX_NUMBER_FIELDS in project template & docs

Also recommend increasing this in the "Integrating into Django" docs.

Fixes #12452

- Don't use commas for thousand separator
- Co-authored-by: Jake Howard <RealOrangeOne@users.noreply.github.com>

docs/getting_started/integrating_into_django.md

@@ -54,6 +54,12 @@ MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
 MEDIA_URL = '/media/'
 ```
 
+Set the `DATA_UPLOAD_MAX_NUMBER_FIELDS` setting to 10000 or higher. This specifies the maximum number of fields allowed in a form submission, and it is recommended to increase this from Django's default of 1000, as particularly complex page models can exceed this limit within Wagtail's page editor:
+
+```python
+DATA_UPLOAD_MAX_NUMBER_FIELDS = 10_000
+```
+
 Add a `WAGTAIL_SITE_NAME` - this will be displayed on the main dashboard of the Wagtail admin backend:
 
 ```python

docs/releases/6.4.md

@@ -15,6 +15,7 @@ depth: 1
 ### Other features
 
  * Add the ability to apply basic Page QuerySet optimizations to `specific()` sub-queries using `select_related` & `prefetch_related`, see [](../reference/pages/queryset_reference.md) (Andy Babic)
+ * Increase `DATA_UPLOAD_MAX_NUMBER_FIELDS` in project template (Matt Westcott)
 
 ### Bug fixes
 
@@ -31,6 +32,7 @@ depth: 1
  * Add the [`wagtail start`](wagtail_start) command to the management commands reference page (Damilola Oladele)
  * Refine the [](project_templates_reference) page sections and document common issues encountered when creating custom templates (Damilola Oladele)
  * Refine page titles to better align with the documentation style guide (Srishti Jaiswal)
+ * Recommend a larger `DATA_UPLOAD_MAX_NUMBER_FIELDS` when [integrating Wagtail into Django](../getting_started/integrating_into_django.md) (Matt Westcott)
 
 ### Maintenance
 
@@ -39,6 +41,17 @@ depth: 1
 
 ## Upgrade considerations - changes affecting all projects
 
+### `DATA_UPLOAD_MAX_NUMBER_FIELDS` update
+
+It's recommended that all projects set the `DATA_UPLOAD_MAX_NUMBER_FIELDS` setting to 10000 or higher.
+
+This specifies the maximum number of fields allowed in a form submission, and it is recommended to increase this from Django's default of 1000, as particularly complex page models can exceed this limit within Wagtail's page editor:
+
+```python
+# settings.py
+DATA_UPLOAD_MAX_NUMBER_FIELDS = 10_000
+```
+
 ## Upgrade considerations - deprecation of old functionality
 
 ## Upgrade considerations - changes affecting Wagtail customizations

wagtail/project_template/project_name/settings/base.py

@@ -156,6 +156,10 @@ STORAGES = {
     },
 }
 
+# Django sets a maximum of 1000 fields per form by default, but particularly complex page models
+# can exceed this limit within Wagtail's page editor.
+DATA_UPLOAD_MAX_NUMBER_FIELDS = 10_000
+
 
 # Wagtail settings