title: How to request object.id in form clean data funtion
body: <p>Have a models:</p>
  
  <pre><code>class Product(models.Model):
      user = models.ForeignKey(User, on_delete=models.CASCADE)
      name = models.CharField(max_length=50)
      variation_1 = models.BooleanField(default=True)
      variation_2 = models.BooleanField(default=True)
      variation_3 = models.BooleanField(default=True)
  
  
  class Order(models.Model):
      buyer = models.ForeignKey(User, related_name='buyer')
      product = models.ForeignKey(Product)
      variations_select = models.CharField(max_length=50, choices=VARIATIONS)
  </code></pre>
  
  <p><strong>in forms.py</strong></p>
  
  <pre><code>class OrderForm(forms.ModelForm):
      variations_select = forms.ChoiceField(choices=VARIATIONS)
  
      class Meta:
          model = Order
          fields = [
              'variations_select'
          ]
  </code></pre>
  
  <p>i need to create a clean function that will check if <code>variation_1</code> or <code>variation_2</code> or <code>variation_3</code> are availiable in <code>Product</code>. For this a need request <code>Product.id</code> to  <code>def clean_variations_select(self):</code> How to do this?</p>
  
  <pre><code>def clean_variations_select(self):
      product = Product.object.get(id = product.id)
      variations_select = self.cleaned_data.get("variations_select")
          if variations_select == "Variation_1" and product.variation_1 == False:
                  raise forms.ValidationError("variation_1 was sold already")
          else:
                  return variations_select
  </code></pre>
  
  <p><code>product = Product.object.get(id = product.id)</code> - don't work cause Order isn't created to database yet(but in rendering view link to new order creation i have that ../product.id/new_order). </p>