d11n

While reviewing #3991 I noticed that we can also improve the current state a bit with regards to values getting unset: Right now the assumption is, that the values get...

Let‘s do this in v1.8: with v1.7 we‘ll ship the op-in checkout as a first instantiation of the new white-labeling approach. With v1.8 we can then maybe switch to the...

@Kukks I think we'd need to change the `AppType` to a string then, because the enum isn't extendible and there are some places that use the enum.

Back into draft mode, still need to convert the public views and parts of the app controllers.

@Kukks the majority of changes is moved files, the rest of the changes update the references to account for the movements. To allow for custom apps we'd have to change...

Just as a reference: [Bootstrap 5 plans to support RTL too](https://blog.getbootstrap.com/2020/06/16/bootstrap-5-alpha/#coming-soon-rtl-offcanvas-and-more).

More context: Bootstrap v5 now supports RTL, the checkout invoice page still uses Bootstrap v3 and this would be an opportunity to update that.

That'd also be a huge step towards #2227 👍

I don't see it in this release, I think that was also the reason why we split it.

I've rebased this PR and updated the info icons. My impression is, that the icon is a bit too small, so that we need to bump its size, which doesn't...