Custom `INVITATION_MODEL` with unique_together fields

I'm working on a multi-tenant app using django-tenants and django-tenant-users, the custom user model is build around this abstract model. Everything works great.

Now I need to implement invitations, but in my case, the invitations should be unique by email+tenant because a user can be invited to the system and to different tenants (I would figure the logic to make this happen in the future). So I tried to create a custom INVITATION_MODEL this way:

users/models.py:

# ...
from tenant_users.tenants.models import UserProfile

class User(UserProfile):
    ROLES = [
        ('ADMIN', 'Administrator'),
        ('SPECIALIST', 'Specialist'),
        ('ASSISTANT', 'Assistant'),
    ]
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    role = models.CharField(max_length=30, choices=ROLES)

    def __str__(self):
        return self.email

class Invitation(AbstractBaseInvitation):
    email = models.EmailField()
    tenant = models.ForeignKey(   # <--- this is the tenant to which the invitation should be tied to
        Tenant,
        on_delete=models.CASCADE,
        editable=False
    )
    created = models.DateTimeField(default=timezone.now)

    class Meta:
        unique_together = ['email', 'tenant']  # <--- unique together

    @classmethod
    def create(cls, email, inviter=None, **kwargs):
        # ...

    def key_expired(self):
        # ...

    def send_invitation(self, request, **kwargs):
        # ...

    def __str__(self):
        return f"Invite: {self.tenant.name} - {self.email}"

Pretty much the same as the default model but just adding the extra tenant field. Added the INVITATION_MODEL to the settings.

I tried manage.py migrate and/or manage.py makemigration but I get this error:

invitations.Invitation.inviter: (fields.E304) Reverse accessor 'User.invitation_set' for 'invitations.Invitation.inviter' clashes with reverse accessor for 'users.Invitation.inviter'.
	HINT: Add or change a related_name argument to the definition for 'invitations.Invitation.inviter' or 'users.Invitation.inviter'.
users.Invitation.inviter: (fields.E304) Reverse accessor 'User.invitation_set' for 'users.Invitation.inviter' clashes with reverse accessor for 'invitations.Invitation.inviter'.
	HINT: Add or change a related_name argument to the definition for 'users.Invitation.inviter' or 'invitations.Invitation.inviter'.

Any idea how can I fix it? Or you know a better approach (or lib) to implement invitations in a multi-tenancy app?

This happened to me because I had messy migrations because of the multiple trials. Drop the DB tables of the previous invitations tables (under your app or the django-invitations app) and it should work later

The same thing happened to me! It seems the problem is, that even when you are setting your invitation model via. INVITATIONS_INVITATION_MODEL, invitation.Invitation is NOT excluded from the migration. After adding this modelfield I was able to create the migration file:

 inviter = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name='+'
 )

But when running manage.py migrate, the invitations default migrations are applied as well. Any help?

You can prevent the migrations from being installed by:

https://docs.djangoproject.com/en/dev/ref/settings/#migration-modules

MIGRATION_MODULES = {
    "invitations": None,
}

But the problem is it screws up pytest because it's always trying to do a DB reference with the Invitation model via migration. The only way I've been able to keep it out is use pytest --no-migrations which takes the models as-defined and builds a schema.

In theory this shouldn't make a difference, running through the migrations or simply using the models to build up the DB, but it feels wrong to be forced into this position.

The best would be to exclude invitations.Invitation when INVITATIONS_INVITATION_MODEL is set to something else, but I do not know, if that is possible.

The next best would be to allow both classes to coexist without overwriting inviter. (Which is a nice work-around. Thanx, @ruphoff!) That could be achieved (as described here: https://docs.djangoproject.com/en/4.2/topics/db/models/#abstract-related-name) with:

class AbstractBaseInvitation(models.Model):
    [...]
    inviter = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.CASCADE,
        related_name="%(app_label)s_%(class)ss",
        related_query_name="%(app_label)s_%(class)s",
    [...]