title: How to show name of the foreign key field instead of its id?
body: <p>I need to show the names of 'user_permissions' instead of their id's.</p>
  <p>Serializers.py :</p>
  <pre><code>class UserSerializer(serializers.ModelSerializer):
      class Meta:
          model = User
          fields = ('id', 'first_name', 'last_name', 'username', 'email','password','is_active', 
                   'date_joined', 'groups', 'user_permissions')
          extra_kwargs = {'username' : {'read_only': True},'password': {'write_only': True}, 'is_active': 
                         {'read_only': True}, 'date_joined': {'read_only': True}, 'groups':{ 'read_only' : 
                          True} , 'user_permissions':{ 'read_only' : True} }
  </code></pre>
  <p>Views.py:</p>
  <pre><code>class UserViewSet(viewsets.ModelViewSet):
      queryset = User.objects.all() 
      serializer_class = UserSerializer
  </code></pre>