Add scanner support to accept deposit return vouchers (Apps-1642, Apps-1645)

[Fabtron]

Deposit return vouchers can now be scanned. This means their accepted and a matching line item is added to the shopping cart. The violation handling has been integrated to ensure that the new feature behavous correctly.

This PR does not contain any ui.

APPS-1642 / APPS-1645

How to test?

Integrate this branch into an app usinng deposit return vouchers.

Test out at least the following.

1. Scan the top 3 items from the link and add products. Trigger the checkout once you have a positive price.
2. Scan an item multiple times -> A violation message pops up handling the douplicated.
3. Scan the already redeemed -> A violation message pops up handling the already redeemed.

Don't scan the zero amount or the redemption failed! We cannot handle it atm.

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, ...)

[cmaier]

Some improvements to the functional approaches. 👍