BindingEventRequest represents input bindings event.
BindingEventResponse includes operations to save state or
send data to output bindings optionally.
InvokeRequest is the message to invoke a method with the data.
InvokeResponse is the response message inclduing data and its content type
from app callback.
ListInputBindingsResponse is the message including the list of input bindings.
ListTopicSubscriptionsResponse is the message including the list of the subscribing topics.
TopicEventRequest message is compatiable with CloudEvent spec v1.0.
TopicEventResponse is response from app on published message
TopicSubscription represents a topic and it’s metadata (session id etc.)