Improve RelatedField and callable default handling

- callable default values will now be properly called 
  - PrimaryKeyRelatedField and SlugRelatedField will now return an appropriate type based on the relation model's Field
  - mock views now have a request object bound even when public is True

testproj/users/serializers.py

@@ -1,19 +1,22 @@
 from django.contrib.auth.models import User
 from rest_framework import serializers
 
+from articles.models import Article
 from snippets.models import Snippet
 
 
 class UserSerializerrr(serializers.ModelSerializer):
     snippets = serializers.PrimaryKeyRelatedField(many=True, queryset=Snippet.objects.all())
+    article_slugs = serializers.SlugRelatedField(read_only=True, slug_field='slug', many=True, source='articlessss')
     last_connected_ip = serializers.IPAddressField(help_text="i'm out of ideas", protocol='ipv4', read_only=True)
     last_connected_at = serializers.DateField(help_text="really?", read_only=True)
 
     class Meta:
         model = User
-        fields = ('id', 'username', 'email', 'snippets', 'last_connected_ip', 'last_connected_at')
+        fields = ('id', 'username', 'email', 'articles', 'snippets',
+                  'last_connected_ip', 'last_connected_at', 'article_slugs')
 
 
 class UserListQuerySerializer(serializers.Serializer):
-    username = serializers.CharField(help_text="this field is generated from a query_serializer")
-    is_staff = serializers.BooleanField(help_text="this one too!")
+    username = serializers.CharField(help_text="this field is generated from a query_serializer", required=False)
+    is_staff = serializers.BooleanField(help_text="this one too!", required=False)