start
Starts the dispatcher by subscribing to the message flux.
This method initiates message processing by subscribing to the messageFlux. Messages are grouped by their grouping key for parallel processing, with each group being handled on the configured scheduler. The dispatcher subscribes to the processing pipeline for error handling.
The subscription can be cancelled gracefully using stopGracefully().
See also
for graceful shutdown
for grouping logic
Throws
if subscription fails or initial setup encounters errors