django.db.utils.ProgrammingError: foreign key referenced-columns list must not contain duplicates

Hello all,

**Quick summary**

I'm getting

`django.db.utils.ProgrammingError: foreign key referenced-columns list must not contain duplicates` when I attempt to run any migrations at all on a new starter project.}

I think there must be something basic I'm missing, but I can't find it in issues or documentation.

**Detailed**

I'm trying to get a basic starter case going and I can't get a single migration to work, so I think I'm missing something simple

```
from django_multitenant.models import TenantModel
from django.db import models

class Account(TenantModel):
name = models.CharField(max_length=255)
contact_info = models.TextField()

class TenantMeta:
tenant_field_name = "id"

class Meta:
unique_together = ["id"]

def __str__(self):
return self.name
```

I create a basic Account tenant.

I then try to add it to the users with database backend enabled. I get a basic user migration

```
class User(TenantModelMixin, AbstractBaseUser, PermissionsMixin, IndexedTimeStampedModel):
email = models.EmailField(max_length=255, unique=True)
is_staff = models.BooleanField(
default=False, help_text=_("Designates whether the user can log into this admin site.")
)
is_active = models.BooleanField(
default=True,
help_text=_(
"Designates whether this user should be treated as "
"active. Unselect this instead of deleting accounts."
),
)
name = models.CharField(max_length=255)
# Custom fields
account = models.ForeignKey(
Account,
on_delete=models.CASCADE,
related_name="users",
null=True,
blank=True,
)
tenant_id = "account_id"
objects = UserManager()

USERNAME_FIELD = "email"

class Meta:
unique_together = ["id", "account"]

```
```

class Migration(migrations.Migration):
initial = True

dependencies = [
("auth", "0012_alter_user_first_name_max_length"),
("accounts", "0001_initial"),
]

operations = [
migrations.CreateModel(
name="User",
fields=[
(
"id",
models.BigAutoField(
auto_created=True, primary_key=True, serialize=False, verbose_name="ID"
),
),
("password", models.CharField(max_length=128, verbose_name="password")),
(
"last_login",
models.DateTimeField(blank=True, null=True, verbose_name="last login"),
),
(
"is_superuser",
models.BooleanField(
default=False,
help_text="Designates that this user has all permissions without explicitly assigning them.",
verbose_name="superuser status",
),
),
(
"created",
model_utils.fields.AutoCreatedField(
db_index=True,
default=django.utils.timezone.now,
editable=False,
verbose_name="created",
),
),
(
"modified",
model_utils.fields.AutoLastModifiedField(
db_index=True,
default=django.utils.timezone.now,
editable=False,
verbose_name="modified",
),
),
("email", models.EmailField(max_length=255, unique=True)),
(
"is_staff",
models.BooleanField(
default=False,
help_text="Designates whether the user can log into this admin site.",
),
),
(
"is_active",
models.BooleanField(
default=True,
help_text="Designates whether this user should be treated as active. Unselect this instead of deleting accounts.",
),
),
(
"account",
django_multitenant.fields.TenantForeignKey(
blank=True,
null=True,
on_delete=django.db.models.deletion.CASCADE,
related_name="users",
to="accounts.account",
),
),
(
"groups",
models.ManyToManyField(
blank=True,
help_text="The groups this user belongs to. A user will get all permissions granted to each of their groups.",
related_name="user_set",
related_query_name="user",
to="auth.group",
verbose_name="groups",
),
),
(
"user_permissions",
models.ManyToManyField(
blank=True,
help_text="Specific permissions for this user.",
related_name="user_set",
related_query_name="user",
to="auth.permission",
verbose_name="user permissions",
),
),
],
options={
"unique_together": {("id", "account")},
},
bases=(django_multitenant.mixins.TenantModelMixin, models.Model),
),
]

```

And it fails because of the double account_id: `foreign key referenced-columns list must not contain duplicates`

```
CREATE TABLE "users_user" ("id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, "password" varchar(128) NOT NULL, "last_login" timestamp with time zone NULL, "is_superuser" boolean NOT NULL, "created" timestamp with time zone NOT NULL, "modified" timestamp with time zone NOT NULL, "email" varchar(255) NOT NULL UNIQUE, "is_staff" boolean NOT NULL, "is_active" boolean NOT NULL, "account_id" bigint NULL);
CREATE TABLE "users_user_groups" ("id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, "user_id" bigint NOT NULL, "group_id" integer NOT NULL);
CREATE TABLE "users_user_user_permissions" ("id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY, "user_id" bigint NOT NULL, "permission_id" integer NOT NULL);

-- The bad lines:
ALTER TABLE "users_user" ADD CONSTRAINT "users_user_id_account_id_e2e2a14b_uniq" UNIQUE ("id", "account_id");
ALTER TABLE "users_user" ADD CONSTRAINT "users_user_account_id_account_i_985fcd95_fk_accounts_" FOREIGN KEY ("account_id", "account_id") REFERENCES "accounts_account" ("id", "id") DEFERRABLE INITIALLY DEFERRED;
```

I can't find any other issues related to this so I think I'm just missing something very simple. Could someone point me in the right direction?

Start with the Account and User model definitions, especially TenantMeta, TenantForeignKey, and each model's unique_together, then inspect the generated initial migration and the PostgreSQL SQL shown in the report. Trace how the migration creates the foreign key and determine why account_id is emitted twice. Done means the starter project's migrations run successfully without duplicate referenced columns.

Written by the indexing model from the issue text.