added an appId to the Guest entity as well an and API registration method to keep track of guests that have been created by partner apps
added a 'registrationAllowed' flag to Application to allow select partner apps to register new guests
make it possible to create an AuthorizationToken directly (without user interaction)
A POJO to describe just the needed info about an authorisation token to a client
make it possible to retrieve an application by app secret
added a registration endpoint for select partner apps