Promotion error messages not localized

[AltayAkkus]

PHP Version

trunk

Shopware Version

trunk

Expected behaviour

Error messages (like "End date needs to be after the start date") should be localized to the users language

Actual behaviour

Only the english messages are shown

How to reproduce

1. Create a random promotion and cause a error (place the end date before the start date)
2. See that the text is english

This because here
https://github.com/shopware/platform/blob/e91d42f995e192aac6f2504a950ad55fb9b13ccc/src/Core/Checkout/Promotion/Validator/PromotionValidator.php#L245-L251
and all the other buildViolation calls a snippet key is defined, but the snippet is not, so the default english fallback is used.