Documentation on how to tie in private composer package repository

[RedUhl]

I'm trying to add the settings to allow composer in the webserver to call out to a private php package repo. The problem that I'm having is that all the documentation I have found references the Dockerfile. Unfortunately I don't see that in setup / configs.

Is your feature request related to a problem? Please describe.
No, but this is not a bug either, its just my lack of knowledge.

Describe the solution you'd like
I'd like to know how to tell the container to refer to my ssh keys or know where to specifically place the keys to access my gitea server.

Describe alternatives you've considered
I'd be happy if you simply pointed me any documentation that I failed to find using google.

Additional context
I am a rank Noob with docker. I love what you have and got it to work. I just need to get composer to pull the proprietary packages. I have docker desktop running on a Mac.

[mgrechanik]

You need to look for webserver image to /bin/ folder.
Are you trying just to pass ssh keys to webserver container?
It would be good to see working recipe if you succeded. Thanks.