Support new C8 ZeebeUser Tasks

[zambrovski]

Scenario

• Library version: 0.1.1
• Camunda version: 8.5
• Description of your use case: I want to use Zeebe User Tasks, as they are available in Camunda 8.5.

Current Behaviour

• New Zeebe User Tasks are currently not delivered by SUBSCRIPTION_REFRESHING delivery strategy of C8 adapter.

Wanted Behaviour

• Support Zeebe User Tasks via Zeebe API (no community clients).

Possible Workarounds

• Use Community Task list client and TASKLIST delivery strategy.

[zambrovski]

Currently blocked, because user tasks query is not possible using Zeebe Client Java in 8.5.x (eventually possible with 8.6.x)