title: How to save ProductAttributesValues in Django Oscar Commerce
body: <p>I'm trying to save m2m relation in Product model on Django Oscar Commerce package, the model has an many to many relation through the ProductAttributeValues model.</p>
  <p>Making Postan POST method query to url <code>127.0.0.1:8000/api/products/1/update/</code>
  serializers.py:</p>
  <pre><code>class ProductAttributeValueSerializer(OscarModelSerializer):
    class Meta:
      model = ProductAttributeValue
      fields = '__all__'
  
  class ProductSerializer(OscarModelSerializer):
    attribute_valuess = ProductAttributeValueSerializer(many=True, read_only=False)
    class Meta:
      model = catalogue_models.Product
      fields = '__all__'
  </code></pre>
  <p>The json content:</p>
  <pre><code>{
    'title': 'Producto 4',
    'is_public': True,
    'description': 'descripción',
    'attribute_values': [
      {'value_text': 'contenido', 'attribute': 1, 'product': 1},
      {'value_text': 'contenido', 'attribute': 2, 'product': 1}
    ]
  }
  </code></pre>
  <p>The postman return this json:</p>
  <pre><code>{
    &quot;attribute_values&quot;: [
      {
        &quot;non_field_errors&quot;: [
          &quot;The fields attribute, product must make a unique set.&quot;
        ]
      },
      {
        &quot;non_field_errors&quot;: [
          &quot;The fields attribute, product must make a unique set.&quot;
        ]
      }
    ]
  }
  </code></pre>
  <p>Anybody could help me please ?
  Thanks in advance.</p>