Get the identity assigned to this interface.
E.g. on Steam, this is the user's SteamID, or for the gameserver interface, the SteamID assigned
to the gameserver. Returns false and sets the result to an invalid identity if we don't know
our identity yet. (E.g. GameServer has not logged in. On Steam, the user will know their SteamID
even if they are not signed into Steam.)
Get the identity assigned to this interface. E.g. on Steam, this is the user's SteamID, or for the gameserver interface, the SteamID assigned to the gameserver. Returns false and sets the result to an invalid identity if we don't know our identity yet. (E.g. GameServer has not logged in. On Steam, the user will know their SteamID even if they are not signed into Steam.)