Don't let people do a multi user install into their /home/user folder

[fryfrog]

Hi,

I do a lot of support for sonarr, radarr and all the many applications in one of these stacks. We're starting to have people show up on Discord having used your script to get going. But they're often storing their media and their docker configs in their ~/, but trying to do a multi user setup.

Can you fix this? The route I would go is if they choose a folder in their home folder, do a one user setup. If they pick a folder not in their home folder, like /docker for configs and /media for downloads and library do multi user. Or you could only allow multi user and block using /home.

Also, it feels like you're using UID in the 13000 range to try and avoid collisions. Why not just use the system's built in useradd and groupadd, then get those IDs to use?