Module DAV don't accept any username

I enabled DAV Module and follwed the installation instructions at

Saying

But whatever username password is set on the https authentification at */dav/filserver.php
Dollibar SuperAdmin or other Dolibarr admin or Webhost-Admin - No username and password is accepted.
But there is also no error message at no level about that could give a hint.
I allow me to consider this as a bug for there is no clear explanation how to make the DAV-Module run.

Hi, ChoY, Did you solve this issue? I meet the same problem that DAV service login always failed.

No, the problem stays unsolved. My possible explanation:
I work on an apache server with a fast-cgi configuration. I read anywhere that this needs a special configuration with Sabre/DAV.
But I use in between as alternative the external module CDAV Also working Sabre/DAV. And here is all good.
So I just hope that one day the dolibarr developers behind DAV will check this bug. Until then see this module CDAV.