[ssi-abstraction] Get a clear outline of the exposed functionality
Before when the rest agent was exposed, everything was open to be used without any restrictions. Now that we do not do that anymore, and the NATS events have to be exposed explicitly, we can limit the functionality and provide simpler APIs. This ticket will be about checking which functionality must be exposed and defining simple interfaces for them. There will not be a focus on a unified API as this will make the API too complex and will not be able to scale in the future.