title: Django Rest Framework - object of type 'type' is not json serializable error
body: <p>I am creating rest api using Django Rest Framework. I am using Djanfo 2.0.5 and python 3. I am getting error "Object of type 'type' is not JSON serializable." at the time of submitting form in browser. I tried with POSTMAN and also getting same error. I have attached snaps of my code of model, serializers and view classes.</p>
  
  <pre class="lang-python prettyprint-override"><code>from django.db import models
  
  # Create your models here.
  
  
  class User(models.Model):
  
      full_name = models.CharField(max_length=255, blank=False)
      email = models.EmailField(blank=False, unique=True)
      password = models.CharField(max_length=100, blank=False)
      profile_pic = models.FileField()
      age = models.CharField(max_length=3, blank=False)
      location_lat = models.CharField(max_length=100, blank=False)
      location_long = models.CharField(max_length=100, blank=False)
      address = models.CharField(max_length=255, blank=False)
      experience_level = models.CharField(max_length=50, blank=False)
      utr_rating = models.CharField(max_length=50, blank=False)
      match_price = models.IntegerField
      auth_token = models.CharField(max_length=100, blank=False, unique=True)
      fb_token = models.CharField(max_length=100, unique=True)
      date_created = models.DateTimeField(auto_now_add=True)
      date_modified = models.DateTimeField(auto_now=True)
  
      def __str__(self):
          return "{}".format(self.full_name)
  </code></pre>
  
  <pre class="lang-python prettyprint-override"><code>from rest_framework import serializers
  from .models import User
  
  
  class UserSerializer(serializers.ModelSerializer):
      class Meta:
          model = User
  
          fields = ('id',
                    'full_name',
                    'email',
                    'password',
                    'profile_pic',
                    'age',
                    'location_lat',
                    'location_long',
                    'address',
                    'experience_level',
                    'utr_rating',
                    'match_price',
                    'auth_token',
                    'fb_token',
                    'date_created',
                    'date_modified')
          read_only_fields = ('date_created', 'date_modified', 'profile_pic')
  </code></pre>
  
  <pre class="lang-py prettyprint-override"><code>from rest_framework import generics
  from .serializers import UserSerializer
  from .models import User
  
  
  class CreateUser(generics.ListCreateAPIView):
      queryset = User.objects.all()
      serializer_class = UserSerializer
  
      def perform_create(self, serializer):
          serializer.save()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/vS67j.png" rel="nofollow noreferrer">Traceback</a></p>