title: Django redundant user relation in related models for permission purposes
body: <p>I am pretty new to django and backend, I made two models <code>Car &amp; Service</code> which have a relation to user (to check permissions, while operating on them) and now I am trying to relate one with another, I have noticed they have both user relation, but Service can't exists without Car, so I start wondering if there is any sense of having user relation in Service just for permissions puroposes, or is it better to create separete permissions for every Model:</p>
  <p>Car Model:</p>
  <pre><code>class Car(models.Model):
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      user = models.ForeignKey(User, on_delete=models.CASCADE)
      ...
  </code></pre>
  <p>and Service Mode:</p>
  <pre><code>class Service(models.Model):
      user = models.ForeignKey(User, on_delete=models.CASCADE)
      name = models.CharField(max_length=200)
      car = models.ForeignKey(
          &quot;cars.Car&quot;,
          on_delete=models.CASCADE,
          related_name=&quot;services&quot;,
      )
  </code></pre>
  <p>and permission used in both API views for those models:</p>
  <pre><code>class isAuthorOrReadOnly(permissions.BasePermission):
      def has_object_permission(self, request, view, obj):
          if request.method in permissions.SAFE_METHODS:
              return True
          return obj.user == request.user
  </code></pre>
  <p>What would be your advice in this scenario ?</p>