Foreign key to settings.AUTH_USER_MODEL causes hard-coded alteration in migration

[Andrew Chen Wang]

We have a model in a package called [django-oauth-toolkit](​https://github.com/jazzband/django-oauth-toolkit/blob/0204383f7b6f8739322f2009f2bb25e8ac9bced2/oauth2_provider/models.py#L78)

Our model for reproduction:

class RefreshToken(models.Model):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="%(app_label)s_%(class)s"
    )

Users of the package are running makemigrations and having to see something like this (ref: ​https://github.com/jazzband/django-oauth-toolkit/issues/1037):

migrations.AlterField(
            model_name='refreshtoken',
            name='user',
            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='%(app_label)s_%(class)s', to='auth.user'),
        ),

Specifically, to='auth.user' is the issue. Our previous migrations properly had to=settings.AUTH_USER_MODEL. Please let me know how to fix this or whether this is a bug. Thanks!