Service responsible for interaction with one or more VPAs (voice personal assistants). Its role is to ensure that each VPA does not interfere with another and that commands to and from a VPA go to the right UI / VPA adaptation. A VPA frontend must use this service to interact with a VPA engine.
Indicates to clients whether each VPA known to the system is in a state that allows it to respond to API calls in this service. If the state is VpaAvailabilityState.AVAILABLE, then the client can check its other states such as the vpaAuthenticationStatus and vpaConversationStates to know that it can indicate to the end-user about, for example, whether they can log in or speak to the VPA.