fix(medusa): quantity prices for line item updates (#5137)

* initial code push

* update metadata and only merge if the existing line item allows merging

* update should_merge check

* undo changes to taxrate service

* update results with unit pricing corresponding to the db values after update

* add should_merge property to line_item creation

* add should_merge property to line_item creation

* fix unit tests

* undo adding "should_merge" to create-line-item

* undo change to "addOrUpdateLineItem"

* :wqh_merge from generate method

* undo changes to unit tests

* revert to adding pricing in updateLineItem method

* update cart service test

* Create funny-radios-juggle.md

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Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

integration-tests/factories/simple-price-list-factory.ts

@@ -16,6 +16,8 @@ type ProductListPrice = {
   currency_code: string
   region_id: string
   amount: number
+  min_quantity?: number
+  max_quantity?: number
 }
 
 export type PriceListFactoryData = {