[unix] Link a Passwd object with a user

unix/models.py

+from django.conf import settings
 from django.db import models
 from django.utils.translation import gettext_lazy as _
 
 
 class Passwd(models.Model):
+    user = models.OneToOneField(
+         settings.AUTH_USER_MODEL,
+         on_delete=models.PROTECT,
+         related_name='unix',
+         verbose_name=_("user"),
+    )
     uid = models.CharField(
         max_length=32,
         verbose_name=_("user ID"),