Async decoupling of Camunda history events

• register a HistoryEventHandler that just forwards HistoryEvents via ApplicationEventPublisher.
• implement a TransactionalEventListener that forwards the receided events to the DbHistoryEventHandler after the original transaction commits.

not working so far!

• start the spring application
• open the h2-console in the browser (http://localhost:8080/h2-console , url: jdbc:h2:mem:camunda-history-async, user&pw:sa)
• query act_hi_actinst .... empty
• open cockpit (http://localhost:8080/, user&pw:admin)
• start process manually in tasklist
• check act_hi_actinst in h2 again ...

see https://forum.camunda.org/t/async-history-event-handler-can-it-work/25589