Allow Production Order to be created with items that have valuation rate as 0

[vijaywm]

Use case:

Book is manufactured with paper supplied by client.

• Create raw material with standard rate = 0 , valuation rate = 0
• Make Stock Entry (Receipt) for material received from client
• Create a Product & BOM for the Product with raw material created above
• Create Production order for the BOM, raw material created in step 1
• Start Production Order & make Stock Entry

Cannot create Production order as required item has 0 valuation rate.

Required an option for 0 valuation rate in Production Order Item similar to Stock Entry Item

If the field allow_zero_valuation_rate is created in Production Order Item, existing method in stock_entry.py will allow Stock Entry to be created when the flag is set to 1.

[jcbdigitalhub]

I think this should be an Item setup? There will always be items with 0 valuation rate such as obsolete items, items from scrap, etc.