User Task default implementation is incompatible with Camunda <8.5

[barmac]

Describe the bug

Camunda 8.4 is still supported, yet the Modeler forces user task to have incompatible implementation type. This is especially painful because deployment in such case is NOT rejected, but rather the new value is ignored by the engine.

Steps to reproduce

1. Set execution platform to 8.4
2. Create a user task
3. The implementation is set to unsupported Camunda User Task

Expected behavior

Job worker implementation for <8.4.

Environment

• OS: [e.g. MacOS 10.2, Windows 10]
• Camunda Modeler Version: [e.g. 2.0.0]
• Execution Platform: [e.g. Camunda 7, Camunda 8]
• Installed plug-ins: [...]

Additional context

Related to https://github.com/camunda/web-modeler/issues/12423

This needs to be implemented in camunda-bpmn-js-behaviors.

[nikku]

Is this found and reported by users (to date)? How long will we still support 8.4?

[barmac]

Found and reported by QA. Support ends in July: https://docs.camunda.io/docs/reference/announcements/#camunda-84

[barmac]

Decision: Move it to the backlog and await further feedback.