Po barcode scan (#458)

* Refactor existing barcode scan endpoint

- Break out into new file just for purchase orders

* Handle scanning of salesorder

* Add new handler for adding items to PO via barcode

* Allocate with barcode

* Add new string

lib/l10n/app_en.arb

@@ -1057,6 +1057,9 @@
   "@scanBarcode": {
   },
 
+  "scanSupplierPart": "Scan supplier part barcode",
+  "@scanSupplierPart": {},
+
   "scanIntoLocation": "Scan Into Location",
   "@scanIntoLocation": {},