WIP django3.2 python 3.10 support

[JensTimmerman]

I started working on porting to django 3.2 but currently stuck on

django-admin migrate   
Traceback (most recent call last):
  File "/home/jens/.local/bin/django-admin", line 8, in <module>
    sys.exit(execute_from_command_line())
  File "/home/jens/.local/lib/python3.10/site-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
    utility.execute()
  File "/home/jens/.local/lib/python3.10/site-packages/django/core/management/__init__.py", line 395, in execute
    django.setup()
  File "/home/jens/.local/lib/python3.10/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/jens/.local/lib/python3.10/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/home/jens/.local/lib/python3.10/site-packages/django/apps/config.py", line 301, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib64/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/jens/workplace/ralph-ng/src/ralph/access_cards/models.py", line 13, in <module>
    from ralph.back_office.models import autocomplete_user
  File "/home/jens/workplace/ralph-ng/src/ralph/back_office/models.py", line 19, in <module>
    from ralph.assets.models.assets import (
  File "/home/jens/workplace/ralph-ng/src/ralph/assets/models/__init__.py", line 1, in <module>
    from ralph.assets.models.assets import (
  File "/home/jens/workplace/ralph-ng/src/ralph/assets/models/assets.py", line 15, in <module>
    from ralph.assets.models.base import BaseObject
  File "/home/jens/workplace/ralph-ng/src/ralph/assets/models/base.py", line 9, in <module>
    from ralph.lib.custom_fields.models import (
  File "/home/jens/workplace/ralph-ng/src/ralph/lib/custom_fields/models.py", line 17, in <module>
    from .fields import (
  File "/home/jens/workplace/ralph-ng/src/ralph/lib/custom_fields/fields.py", line 5, in <module>
    from django.contrib.contenttypes.fields import (
ImportError: cannot import name 'ReverseGenericRelatedObjectsDescriptor' from 'django.contrib.contenttypes.fields' (/home/jens/.local/lib/python3.10/site-packages/django/contrib/contenttypes/fields.py)

I will see if I have some time later to look into this