add some new data to device login data, first part of broker to stake holders assignment

apps/pos_device/web/api/v1/serilaizers/device.py

@@ -86,3 +86,9 @@ class StakeHoldersSerializer(ModelSerializer):
         ).data
 
         return representation
+
+
+class BrokerStakeHolderAssignSerializer(ModelSerializer):
+    class Meta:
+        model = pos_models.BrokerStakeHolderAssignment
+        fields = '__all__'