title: Object of type CharField is not JSON serializable
body: <p>I'm learning Django by trying to build what comes to the mind. Now I'm trying to build Django rest API
  that returns item or all items from a postgres data table.</p>
  <p>models.py</p>
  <pre><code>class AdModel(models.Model):
      id = models.IntegerField
      name = models.CharField(max_length=50),
      address = models.CharField(max_length=50),
      web = models.CharField(max_length=50),
  
      class Meta:
          db_table = 'mock_location_data'
  </code></pre>
  <p>serializers.py</p>
  <pre><code>class AdSerializer(serializers.ModelSerializer):
  class Meta:
      model = AdModel
      fields = ['id', 'name', 'address', 'web']
  </code></pre>
  <p>views.py</p>
  <pre><code>class AdAPIView(APIView):
  
      def get(self, request):
          queryset = AdModel.objects.all()
          serializer_class = AdSerializer(queryset, many=True)
          return Response(serializer_class.data)
  </code></pre>
  <p>On GET request I'm getting Internal server error 500 with &quot;Object of type CharField is not JSON serializable&quot;</p>
  <p>in views.py if replace fields = ['id', 'name', 'address', 'web'] with</p>
  <pre><code>fields = '__all__'
  </code></pre>
  <p>I'm getting all the id fields</p>
  <pre><code>[  {    &quot;id&quot;: 1  },  {    &quot;id&quot;: 2  },  {    &quot;id&quot;: 3  },.....]
  </code></pre>
  <p>but no other data</p>
  <p>I'm using Django 3.1.5 and DRF 3.12.2</p>