steam-support interface has been developed specifically to help Valve’s Steam client configure pressure-vessel containers from the Steam snap.
Only the Steam snap may establish this interface. See Introducing early access to the Steam snap for more details.
See Interface management and Supported interfaces for further details on how interfaces are used.
The source code for the Steam snap: https://github.com/canonical/steam-snap
The test code can be found in the snapd repository: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/steam_support_test.go
The source code for the interface is in the snapd repository: https://github.com/snapcore/snapd/blob/master/interfaces/builtin/steam_support.go