Message properties are not reused when a message event template is applied

[barmac]

Describe the bug

When I apply a message event template to an element linked to a message with a defined subscription correlation key, the newly created message does not get the old value.

This is contrary to the expectations that we built in other parts of element templates, e.g. input/output:

Screen.Recording.2025-02-25.at.10.42.55.mov

Steps to reproduce

Screen.Recording.2025-02-25.at.08.24.09.mov

Expected behavior

Subscription correlation key is reused.

Environment

• OS: [e.g. MacOS 10.2, Windows 10]
• Camunda Modeler Version: any with message event templates
• Execution Platform: C8
• Installed plug-ins: [...]

Additional context

SUPPORT-25972

[barmac]

This needs to be fixed in bpmn-io/bpmn-js-element-templates