PricingSetting::INPUT_PRICE_TYPE is not respected on several places

[vitek-rostislav]

Describe the bug

The application allows us to choose the input price type (it can be set in the admnistration admin/superadmin/pricing/). However, when I start using INPUT_PRICE_TYPE_WITHOUT_VAT (typical for B2B stores), I can see several issues:

• QuantifiedProductPriceCalculation::calculatePrice has hardcoded price calculation from price with VAT, which might result in the wrong results - the customer might see badly calculated prices without VAT in the cart
• the same applies to OrderItemPriceCalculation - the customer then sees badly calculated prices of order items in order mail and on the order detail page. Also, the administrator sees the bad prices.

I tried to simulate the problem on the current master version of SSFWCC:

• I set the input price to "Without VAT"
• I created a new VAT with a 19 % rate and set it as default for the SK domain
• I set the SK domain price for Hello Kitty to 5,80 €
• On the SK domain, I put Hello Kitty in the cart, and change the quantity to 3 pcs. One of the problems is (rather UX), I can not see the total price without VAT...However, if it was possible to see it, I would see it is badly calculated to 17,39 € (while it should be 3 x 5,80 = 17,4 €)
• After finishing the order, I can see the item's bad prices in administration (see image 1)
• Also, the order detail on SF is quite weird (see image 2) - the total price without VAT is wrong and the first column with unit price without VAT is labeled as "Unit price with VAT"

Image 1:

Image 2:

[vitek-rostislav]

While digging deeper into this, I would say another problem is that the whole OrderItem::hasForcedTotalPrice() related logic heavily counts on the fact the application uses input prices with VAT 😞 see https://github.com/shopsys/shopsys/blob/13.0/packages/framework/src/Model/Order/Item/OrderItemData.php#L20

[vitek-rostislav]

Another problematic (or questionable, at least) place is here - https://github.com/shopsys/shopsys/blob/13.0/project-base/app/tests/FrontendApiBundle/Test/GraphQlTestCase.php#L250 - the prices in tests are calculated using both approaches (from price with VAT and from price without VAT). I would say it should also respect the application settings 🤔