[FEAT] Make internal listening port for web-ui (3579) configurable as environment variable #122

Is this a new feature request?

• I have searched the existing issues

Wanted change

I would really like to run several instances of OMBI on the same docker host (in the same stack). For that, it would be really nice to be able to have them listen on a different internal port each. (For now, I'm editing the run-files inside the docker containers to make that happen, which is a pain especially after updates obvieously.)

So, not a lot of people want or need this i guess. I thought i'd ask anyway.

Reason for change

To run several instances of OMBI in the same stack, each instance needs to listen on a different internal port, at least in my setup.
I run OMBI inside a stack, that only connects through a gluetun-container (VPN). So, i am not exposing any ports for the OMBI container itself, but just expose ports for the gluetun-container (as you need to do in this case).

Proposed code change

Right now, in "/etc/s6-overlay/s6-rc.d/svc-ombi/run" the port is hard-coded as the default one.
My idea would be to read this port from a docker environment variable. If the environment variable for the internal port is not set, it should default to "3579".