Hi everyone 
I have an app where I can limit to groups for usage.
But, I don’t know where is defined in my project ?
It’s to improve another app, I would like to implement this possibility.
Whether that option is available for an app or not depends on the types specified in appinfo/info.xml. Some types like filesystem/authentication currently don’t allow to limit the app to groups as it would be always loaded for those types.
The list of restricted types can be found here: server/AppManager.php at 66ffedcb1662088007711d132df7a630a313c572 · nextcloud/server · GitHub
A possible solution that some apps implement is to have a custom setting in the app and then check the group membership and manage access permissions on your own.