/backport to stable30

use IAppConfig please :)

If it is fixed now, then I love to. It had a really bad bug that you cannot mix IConfig->setAppValue and e.g. IAppConfig->setValueBool.
Meaning you have to migrate every access to that value to the types access, in every place. Otherwise after using the typed access you can no longer access it with the IConfig variant.

One recent place were we needed to fix this: #46991

@come-nc I refactored this again, but we need to put parts of the migration into a background job. As we need to iterate a list of users which could take long if many users had custom backgrounds.

I reused the logic from the dashboard -> theming repair step / background job.

So it is now working correctly for me:

Screen recording

Setup

After Upgrade to Nextcloud 30 / 31

Please note the wrong colors in the beginning, I triggered the migration then and reload the page:

1. In the beginning the previous primary color is set as background color causes wrong color of icon in the top bar
2. No primary color
3. The admin theming colors are all wrongly reset to default

This is all fixed after the migration + background job ran:

Psalm is quite angry