Improvement
Customers can now add new items to the cart and adjust their quantities without invalidating an already approved quote.
For example, if a quote for 5 units of product A is approved and the customer later adds 3 units of product B, updating product B will not invalidate the approved quote, because B has no quoted price.
However, changing the quantity of product A will invalidate the approved quote, since the approved price was locked to the originally quoted quantity for A.
