Default settings.MIGRATE is missing

[Tobias Krönke]

Heyo! I hope this is an easy one. For being able to easily skip some tests if migrations are turned off, settings.MIGRATE should actually exist, so we are not forced define it in all of our settings files. Currently, the default does not exist in the settings:

>>> from django.conf import settings
>>> settings.MIGRATION_MODULES
{}
>>> settings.MIGRATE
Traceback (most recent call last):
  File "<input>", line 1, in <module>
    settings.MIGRATE
  File "/var/env/lib/python3.10/site-packages/django/conf/__init__.py", line 104, in __getattr__
    val = getattr(_wrapped, name)
AttributeError: 'Settings' object has no attribute 'MIGRATE'

Will create a PR and link it here in a bit.