Union of all message body shapes. Each concrete Message type carries
its specific body type directly, so consumers usually narrow at the message
level (message.type) and never see MessageBody directly. Exported for
tooling that needs to refer to "any body shape" generically.
Union of all message body shapes. Each concrete
Messagetype carries its specific body type directly, so consumers usually narrow at the message level (message.type) and never seeMessageBodydirectly. Exported for tooling that needs to refer to "any body shape" generically.