Allow to use event + pull for C7 Adapter

[zambrovski]

Scenario

• Library version: 0.2.0
• Description of your use case: scheduled-based user task delivery is a good default when used for C7 adapter, because it will eventually deliver all tasks independent from failures etc. In the same time, if the functionality of the application is using Camunda 7 Spring Eventing bridge (e.g. for triggering some process) and is asking UserTaskSupport for any information about the task, it will ultimately fail because the event is always firing before the task is delivered by the schedule. To prevent this, the so called event-scheduled (so a combination of events and pull on schedule) should be possible.

Current Behaviour

Either event-based or schedule-based.

Wanted Behaviour

Event-based and schedule-based at the same time.

Possible Workarounds

None.

[zambrovski]

Initial but not working implementation is in feature/c7_event_pull_delivery