Missing chunk_size throws exception when serializing many-to-many Model field

[Erica Pisani]

Related issue: https://code.djangoproject.com/ticket/35238

I'm currently upgrading a project from v4.x to v5.0.1 and, when attempting to save a model with a prefetched many-to-many field, the "ValueError: chunk_size must be provided when using QuerySet.iterator() after prefetch_related()" exception is thrown within the core Django ​serializer:

Here's the trace within my project that leads to the exception:

File ".../site-packages/django/db/models/base.py", line 822, in save
    self.save_base(
  File ".../site-packages/django/db/models/base.py", line 924, in save_base
    post_save.send(
  File ".../site-packages/django/dispatch/dispatcher.py", line 189, in send
    response = receiver(signal=self, sender=sender, **named)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

# The revisions files below are referring to the django-reversion library

  File ".../site-packages/reversion/revisions.py", line 340, in _post_save_receiver
    add_to_revision(instance, model_db=using)
  File ".../site-packages/reversion/revisions.py", line 209, in add_to_revision
    _add_to_revision(obj, db, model_db, True)
  File ".../site-packages/reversion/revisions.py", line 184, in _add_to_revision
    serialized_data=serializers.serialize(
                    ^^^^^^^^^^^^^^^^^^^^^^
  
File ".../site-packages/django/core/serializers/__init__.py", line 134, in serialize
    s.serialize(queryset, **options)
  File ".../site-packages/django/core/serializers/base.py", line 143, in serialize
    self.handle_m2m_field(obj, field)
  File ".../site-packages/django/core/serializers/python.py", line 91, in handle_m2m_field
    queryset_iterator(obj, field),
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../site-packages/django/core/serializers/python.py", line 86, in queryset_iterator
    .iterator()
     ^^^^^^^^^^
  File ".../site-packages/django/db/models/query.py", line 532, in iterator
    raise ValueError(
ValueError: chunk_size must be provided when using QuerySet.iterator() after prefetch_related().

I confirmed that applying the same fix as the issue linked above addresses the issue.

Proposed solution:
I'm happy to put up a pull request with the patch, and can emulate what the issue linked above did which is conditionally supply a chunk_size similar to the solution implemented in the issue linked above'