Creation of a subdomain for alias domain not possible
Summary
If an alias domain exists, no subdomain can be selected (created) for it.
Steps to reproduce
Try to create a new subdomain for an alias domain
Correct behaviour
Alias domains should also be displayed in the subdomain domain selection
Environment
Debian 11 (bullseye) ISPConfig: 3.2.10p2 --use-ftp-ports=40110-40210 --use-php=5.6,7.0,7.1,7.2,7.3,7.4,8.0,8.1,8.2 --no-mailman --no-dns --no-firewall
Output of the command