Improve readability and interpretability of code by explicitly stating null in union types. This
change has been applied across multiple files and functions.

PHP8.4 compatibility

For orders this is not needed. the internal instance cache causes more problems
due to the mix between uuid and id cache. the internal cache on uuid / id was therefore removed.
Orders have the data freshly fetched from the db anyway. therefore unnecessary.
In addition, a wrong order object was repeatedly retrieved when sending mail.

refactor: order process -> new event onOrderProcess; next step -> scroll to top; empty article no considered; shopping card type events

- pagination for my orders in profile
- order address step