Custom config variable in jibri

I am trying to have an additional config variable to the dockerized jibri setup.
I added that extra variable to this file https://github.com/jitsi/docker-jitsi-meet/blob/master/jibri/rootfs/defaults/config.json inside the xmpp_environments object,
I understood that this is being parsed over at https://github.com/jitsi/jibri/blob/master/src/main/kotlin/org/jitsi/jibri/config/JibriConfig.kt.

Assuming that my variable name is abc_def, what changes should I make in the file at https://github.com/jitsi/jibri/blob/99288dc8e6f4b4c74886d31737b05e9e3bfad3c3/src/main/kotlin/org/jitsi/jibri/config/JibriConfig.kt#L58 and https://github.com/jitsi/jibri/blob/99288dc8e6f4b4c74886d31737b05e9e3bfad3c3/src/main/kotlin/org/jitsi/jibri/config/JibriConfig.kt#L119 and how should I consume this variable in some other file in the project?

config.json and JibriConfig are now deprecated, the new config file is jibri.conf, which serves as an overrides files for the defaults located in reference.conf in the repo. What sort of new property are you looking to add?