gconf interface allows access to any item from the legacy GConf configuration system for the current user, typically used by old GNOME desktop libraries and applications.
This interface needs to be manually connected because gconf is a global database for GNOME desktop and application settings and offers no application isolation.
Modern applications should use dconf/gsettings instead and this interface is provided for old codebases that cannot be migrated.
The test code can be found in the snapd repository: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/gconf_test.go
The source code for the interface is in the snapd repository: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/gconf.go