Simple login to Grist core

Hello!
I have been using Grist now for the last 6 months, and am pretty happy with it. So far, I have been using the desktop version.
Now I’d like to expand with some multi-user applications. I installed the core version under Docker, no problem, it works fine.

But I spent several hours trying to understand in the forum how to handle the login matter, in order to differentiate who is logging in. Technically, that specific part is over my head.

But I am looking at a very simple solution: I work on an off-line network, I have a small menu app which first allows users to log with user/password before accessing the menu itself, the menu just shows on the fly the options a user has access to, I’d like to send a proper request to launch the proper Grist app.

Is there a simple solution for that (via API, or another way)?

Thanks in advance!!
Michel