Fix missing updates for the shopping cart (Apps-2163)

[Fabtron]

The viewmodel responsible for managing the shopping cart ony keeps track of the initial project. If the project or the shopping cart changes no updates are triggerd leading to wrong shopping carts displayed for not matching shops.

To fix this the viewmodel now tracks shoppingCart changes that occour inside a project (e.g. if a store is switched) and project changes.

APPS-2163

How to test?

Integrate this branch into a multi retailer App and test out the shopping cart. Create different carts for different shops and projects and check if the cart is always the expected cart. Do some checkouts to see that the right card is used for the checkout.

Definition of Done

• Issue is linked
• All requirements of the issue are fulfilled
• Changelog is updated
• Documentation is updated
• Self-Review
• Review with the Product Owner (Release-Variante o. Minified Build)

App Tests

• Minified build has been tested (aka. Release Build)
• Environments have been taken care of (Production/Staging)
• Supported languages have been tested
• Light-/Dark-Mode has been tested
• Edge-Cases have been tested
• Android API Levels have been taken care of (minSdk?)

Testing

• Tests have been written (aka Unit-Tests, Integration-Tests, ...)