Our DbSelect::where() is not (or no longer?) compatible w/ Zend_Db_Select::where().
DbStore::load() now uses Zend_Db_Select but we should definitely think about our
DbSelect::where() implementation.
fixes#7353
The calculation is still subject to the concrete writer implementation as its
parent Icinga\User\Preferences\PreferencesStore is only an abstraction
layer without any knowledge how the data is actually stored so it is not able
to determine how to handle differences.
fixes#6220
