[BUG] Shift websocket port mapping to application and not NGINX

[thelamer]

Right now you cannot combine multiple desktop containers on the same IP on a network because it is hard wired to 8082 here:

https://github.com/selkies-project/selkies/blob/main/src/selkies/selkies.py#L20

When the user sets a custom port we still need that in nginx to handle subfolders properly, but we should also map the application to the new port.

This also needs documentation as there is no "HTTPS" websocket port, the internal websocket port is always http and you cannot map it to multiple ports. NGINX handles this.

[thelamer]

So this is unavoidable but this will have to be a third parameter with CUSTOM_WS_PORT as the application is designed now. I am not ready to rip the band aid off of ripping out NGINX yet. selkies-project/selkies@a9272cf

With this, need to cleanup our launch options and remove the 8081 port we are setting that is unused and doc the change so people that want to run a bunch of these in a vpn container network can at least set this and be functional.

Also need logic to swap the hard codes in the NGINX config now when you init-nginx.

https://github.com/linuxserver/docker-baseimage-selkies/blob/master/root/etc/s6-overlay/s6-rc.d/init-nginx/run
https://github.com/linuxserver/docker-baseimage-selkies/blob/master/root/defaults/default.conf#L39

[thelamer]

This is completed but will take time to waterfall.