core: add custom group model with hierarchy , add tree admin

passbook/admin/api/v1/groups.py

@@ -0,0 +1,36 @@
+"""passbook admin gorup API"""
+from rest_framework.permissions import IsAdminUser
+from rest_framework.serializers import ModelSerializer, Serializer
+from rest_framework.viewsets import ModelViewSet
+
+from passbook.core.models import Group
+
+
+class RecursiveField(Serializer):
+    """Recursive field for manytomanyfield"""
+
+    def to_representation(self, value):
+        serializer = self.parent.parent.__class__(value, context=self.context)
+        return serializer.data
+
+    def create(self):
+        raise NotImplementedError()
+
+    def update(self):
+        raise NotImplementedError()
+
+class GroupSerializer(ModelSerializer):
+    """Group Serializer"""
+
+    children = RecursiveField(many=True)
+
+    class Meta:
+        model = Group
+        fields = '__all__'
+
+class GroupViewSet(ModelViewSet):
+    """Group Viewset"""
+
+    permission_classes = [IsAdminUser]
+    serializer_class = GroupSerializer
+    queryset = Group.objects.filter(parent__isnull=True)