With what was discussed in The Hague, the unity8 snap should 'slots: [mir]' and then snaps should 'plugs: [unity8, mir]'. The unity8 snap should put the mir socket in /run/user/[0-9]*/mir_socket as specified in mirConnectedPlugAppArmor in interfaces/builtin/mir.go.
With what was discussed in The Hague, the unity8 snap should 'slots: [mir]' and then snaps should 'plugs: [unity8, mir]'. The unity8 snap should put the mir socket in /run/user/ [0-9]*/ mir_socket as specified in mirConnectedPlu gAppArmor in interfaces/ builtin/ mir.go.