Support user task listeners

[barmac]

What should we do?

Implement user task listeners in Camunda 8

<userTask id="my_user_task" name="my_user_task">
 <extensionElements>
   <zeebe:userTask/>
   <zeebe:taskListeners>
     <zeebe:taskListener eventType="create" type="create_listener" retries="2"/>
     <zeebe:taskListener eventType="assignment" type="assignment_listener"/>
     <zeebe:taskListener eventType="update" type="update_listener" retries="8"/>
     <zeebe:taskListener eventType="complete" type="complete_listener"/>
   </zeebe:taskListeners>
   <zeebe:priorityDefinition/>
   <!--other extension props e.g. assignmentDefinition, priorityDefinition-->
 </extensionElements>
 <!--other props-->
</userTask>

• [ ] I can define task listeners on user task
  • [ ] type (string, FEEL expression)
  • [ ] eventType (options to be clarified)
  • [ ] retries (string, FEEL expression, default is 3)
• [ ] (to clarify) I can define task listeners on process
• [ ] (to clarify) Duplicate task listeners are marked as invalid
• [ ] TLs can be used in Camunda 8.7 or newer

Projects:

• [ ] zeebe-bpmn-moddle part
• [ ] bpmn-js-properties-panel part
• [ ] bpmnlint-plugin-camunda-compat part
• [ ] camunda/linting part (error messages, properties panel entries)

Why should we do it?

Product hub epic: https://github.com/camunda/product-hub/issues/1316

[barmac]

This is blocked until we clarify the XML structure: https://camunda.slack.com/archives/C0622NWC9LK/p1729161860084329

[barmac]

We clarified the XML structure, but the list of event types needs to be decided upon yet: https://github.com/camunda/product-hub/issues/1822#issuecomment-2419645986