* refactors function based report views into class based for EIV, OEK, EMA, KOM
* introduces BaseReportView for proper inheritance of shared logic
* refactors generating of qr codes into proper class
* adds proper handling in case of BadRequest (error 400)
* enhances html template for error 500
* adds new html template for error 400
* adds uuid_required decorator to missing views
* updates translations