Allow entering website URLs with special characters / IDN in backend
Overview
Since a couple of years so called internationalized domain names (IDN) are allowed that contain special characters like German Umlauts, chracters from the Arabic alphabet etc. Modern web browsers also support them and so it's no surprise that they are more and more in use. That's why for instance http://münchen.de or http://köln.de are registered domains. However CiviCRM won't accept entering these in the contact screen:
In the case of münchen.de which is forwarded to muenchen.de this would be managable, but from real CiviCRM usecases I know dozends of URLs that don't come with alternatives so users won't get them into their Civi (theoretically they could convert them using an IDN converter so that münchen.de becomes xn--mnchen-3ya.de but in practice this is not a real option).
Current behaviour
Website URLs containing special characters (valid according to IDN standards) cannot be entered in the backend.
Proposed behaviour
Website URLs containing special characters (valid according to IDN standards) can be entered in the backend.