New Validation Logic

[robinmanuelthiel]

This pull request introduces a validation improvement to the BasketItem model in the Basket.API project. It adds a new condition to ensure that the OldUnitPrice is not greater than or equal to the UnitPrice.

Validation improvements:

• src/Basket.API/Model/BasketItem.cs: Added a validation check to the Validate method that triggers an error message ("Der Preis ist zu heiß!") if OldUnitPrice is greater than or equal to UnitPrice.

[Copilot]

Pull Request Overview

Adds a new rule to validate that the old unit price is lower than the current unit price.

• Introduces a check in BasketItem.Validate to compare OldUnitPrice and UnitPrice
• Returns a validation error when the price rule is violated

Comments suppressed due to low confidence (1)

src/Basket.API/Model/BasketItem.cs:22

• Add unit tests for this new validation rule to ensure it correctly enforces that OldUnitPrice < UnitPrice under various scenarios.

        if (OldUnitPrice >= UnitPrice)

[Copilot]

Error message is in German and inconsistent with the existing English messages; consider using a clear English message like "UnitPrice must be greater than OldUnitPrice".

Suggested change

	results.Add(new ValidationResult("Der Preis ist zu heiß!", new[] { "OldUnitPrice", "UnitPrice" }));
	results.Add(new ValidationResult("UnitPrice must be greater than OldUnitPrice", new[] { "OldUnitPrice", "UnitPrice" }));