+=item C<update_part $shop_part $todo>
+
+Updates one Part including all metadata and Images in a Shop.
+Needs a valid 'SL::DB::ShopPart' as first parameter and a requested action
+as second parameter. Valid values for the second parameter are
+"price, stock, price_stock, active, all".
+The method updates either all metadata or a subset.
+Name and action for the subsets:
+
+ price => updates only the price
+ stock => updates only the available stock (qty)
+ price_stock => combines both predecessors
+ active => updates only the state of the shop part
+
+Images should always be updated, regardless of the requested action.
+Returns 1 if all updates were executed successful.
+
+