Declare "from PO" receiving workflow if applicable, in API

tailbone/api/batch/receiving.py

@@ -77,9 +77,15 @@ class ReceivingBatchViews(APIBatchView):
 
     def create_object(self, data):
         data = dict(data)
+
+        # all about receiving mode here
         data['mode'] = self.enum.PURCHASE_BATCH_MODE_RECEIVING
-        batch = super(ReceivingBatchViews, self).create_object(data)
-        return batch
+
+        # assume "receive from PO" if given a PO key
+        if data['purchase_key']:
+            data['receiving_workflow'] = 'from_po'
+
+        return super().create_object(data)
 
     def auto_receive(self):
         """