Registers a username and an app name for licensing purposes. The only data sent by this call is userName and appName. A given username can only be registered once per app session.
Example
var application = fin.desktop.Application.getCurrent();
application.registerUser("user", "myApp",
function() {
console.log("Successfully registered the user");
},
function(err) {
console.log("failure:", err);
}
);