Requesting documentation of consumer_group annotation

Error reported from Kalix system: KLX-00405 Service call [com.example.deal.action.DealTopicService.dealChangeProtoToTopic] and [com.example.deal.action.DealTopicService.dealChangeJsonToTopic] both subscribe to the same event source with the same input type.

To fix this issue, if you wish to define two independent consumers of the same event source, use the consumer_group annotation on the source to identify them.