askvortsov
Thanks,
Looking at the logs, it seems that that file is updated on startup.
It looks like composer.json is referring to the file composer.json at /flarum/app/extensions.
Here is the docker image we are using.
https://github.com/mondediefr/docker-flarum
[INFO] Setting folder permissions
[INFO] Logging to stdout activated
[INFO] Adding (name of my custom plugin) composer repository
...
[INFO] Flarum already installed, init app...
Clearing the cache...
[INFO] Install extra bundled extensions
./composer.json has been updated
Running composer update fof/analytics fof/best-answer fof/gamification fof/links fof/polls fof/upload fof/user-directory
Loading composer repositories with package information