Fixed changing cart item quantity using updateCartItems mutation

[rogyar]

Description (*)

This PR fixes updateCartItems behavior in terms of changing item quantity. It looks like after some refactoring we lost the saving operation upon changing item qty (without changing other item's data).

Fixed Issues (if relevant)

1. 927 : Update quantity for updateCartItems mutation does not work

Manual testing scenarios (*)

1. Create empty cart

mutation {
  createEmptyCart
}

2. Add a simple product to the cart

mutation {
  addSimpleProductsToCart(input: {
    cart_id: "$maskedCartId"
    cart_items: [
      {
        data: {
          quantity: 3,
          sku: "simple"
        }
      }
    ]
  }) {
    cart {
      items {
        id
        quantity
        product {
          name
        }
      }
    }
  }
}

3. Change the quantity of the added item using updateCartItems mutation

mutation {
  updateCartItems(input: {
    cart_id:"$maskedCartId"
    cart_items: [
      {
        cart_item_id: $itemId
        quantity: 5
      }
    ]
  }) {
    cart {
      items {
        id
        quantity
        product {
          name
        }
      }
    }
  }
}

4. Retrieve the cart contents via separate query

{
  cart(cart_id:"$maskedCartId") {
    items {
      id
      quantity
      product {
        name
      }
    }
  }
}

[lenaorobei]

@rogyar could you please cover this case with api-functional test?

[rogyar]

Sure, working on it

[magento-engcom-team]

Hi @lenaorobei, thank you for the review. ENGCOM-5864 has been created to process this Pull Request :eight_spoked_asterisk: @lenaorobei, could you please add one of the following labels to the Pull Request?

Label	Description
Auto-Tests: Covered	All changes in Pull Request is covered by auto-tests
Auto-Tests: Not Covered	Changes in Pull Request requires coverage by auto-tests
Auto-Tests: Not Required	Changes in Pull Request does not require coverage by auto-tests

[lenaorobei]

Unfortunately need to close because the issue was fixed by internal team in 2.3.3-develop branch.