Allow having multiple user_model/remove user_model from HistoricalRecords

[mariusty]

When a project contains multiple user models that can edit the same model, it’s not possible to add history.

The issue arises because HistoricalRecords enforces a single user_model, which doesn’t work when different types of users can modify the same object.

Example:

class BusinessOwnerUser(models.Model):
        name = models.CharField(max_length=150, null=True, blank=True)

class CustomerUser(models.Model):
        name = models.CharField(max_length=150, null=True, blank=True)

class Invoice(models.Model):
        title = models.CharField(max_length=150, null=True, blank=True)
        history = HistoricalRecords()

if a customer user changes the Invoice there is an error
"Cannot assign \"<CustomerUser: 7 7>\": \"HistoricalInvoice.history_user\" must be a \"BusinessOwnerUser\" instance.

I've tried:

• leave the user_model parameter for HistoricalRecords empty
• use BusinessOwnerUser as user_model parameter
• use a list of user_model parameter for HistoricalRecords
• write a custom history_user_setter:

def set_historical_user_none(historical_instance):
    historical_instance.history_user_id = None

I think it would be nice to have an option to disable user_model if needed OR to allow multiple user models to be linked to the historical model.

[Grayknife]

What are the reasons, that you have multiple different user models? Usually its best practice to have only one user model in place 🤔 . What is your AUTH_USER_MODEL in the django settings.py?