# Functions
NewMessageEnvelope creates a new MessageEnvelope for the specified payload with attributes from the specified context.
NewMessageEnvelopeForRequest creates a new MessageEnvelope for sending request to EdgeX via internal MessageBus to target Device Service.
NewMessageEnvelopeForResponse creates a new MessageEnvelope for sending response from Device Service back to Core Command.
NewMessageEnvelopeFromJSON creates a new MessageEnvelope by decoding the message payload received from external MQTT in order to send request via internal MessageBus.
NewMessageEnvelopeWithError creates a new MessageEnvelope with ErrorCode set to 1 indicating there's error and the payload contains message string about the error.
# Structs
HostInfo is the URL information of the host as the following scheme: <Protocol>://<Broker>:<Port>.
MessageBusConfig defines the messaging information need to connect to the message bus in a publish-subscribe pattern.
MessageEnvelope is the data structure for messages.
TopicChannel is the data structure for subscriber.