title: How can i add @property field to django rest serializer with '__all__'
body: <p>I have model </p>
  
  <pre><code>class A(models.Model):
      is_enable = models.BooleanField(default=False)
      title = models.CharField(max_length=255, blank=True, null=True)
      updated_date = models.DateTimeField(auto_now=True)
      show_count = models.IntegerField(default=0)
      answers_count = models.IntegerField(default=0)
      audience = JSONField()
      events = JSONField()
      rules = JSONField()
      message = models.TextField(blank=True)
  
      @property
      def conversion(self):
          if self.show_count == 0:
              return 0.0
          return (self.answers_count / self.show_count) * 100
  </code></pre>
  
  <p>And i have serializer</p>
  
  <pre><code>class ASerializer(serializers.ModelSerializer):
      audience = serializers.JSONField()
      events = serializers.JSONField()
      rules = serializers.JSONField()
  
      class Meta:
          model = Trigger
          fields = '__all__'
  </code></pre>
  
  <p>I want to add to response @property conversion` field
  and I want to do something like this in serializer</p>
  
  <pre><code>class Meta:
              model = Trigger
              fields = '__all__' + conversion
  </code></pre>
  
  <p>I know that i can make something like this</p>
  
  <pre><code>class Meta:
                  model = Trigger
                  fields = ('is_enable', 'title' ... 'conversion')
  </code></pre>
  
  <p>But i want add all fields and conversion field and do this more beautiful</p>