Support for multi domain setups

[EnderArchery]

Hi it would be nice if the built in server would work on a multi domain setup. Currently, only the domain that was used while accessing the admin settings is working.

Unfortunately it's not enough to add other lok allowed domains.
This would... make the code server treat each domain as a new nextcloud instance, allowing the same file to be opened for each of them, without a collaborative session. (resulting in conflicts)

With the docker image, the process is as follows
Set an environment variable called aliasgroup1
set it to
https://<primarydomain>,https://(<secondarydomain>)|(<tertiarydomain>)|....
the primary domain is the one that collabora uses to request the file from nextcloud even if it's one of the aliases.

(Warning, in the newest docker image, this has suddenly stopped working, the aliases aren't allowed to access the server anymore... reason unknown. Maybe it's something to do with the lok functionality and the fact that the aliases are determined using regex... which the lok stuff doesn't support?)