Required form field should be marked as mandatory

This is a 2-fold issue:

• Templates accept a constraint notEmpty set to TRUE, but ECA is not including that in its plugin template definitions yet. This needs to be addressed in ECA and the related issue for that is 📌 Define required constraint for BPMN based modellers Fixed
• With the constraint being defined correctly, bpmn.io is properly showing an error message when a field remains empty, but they have no indicator for required fields. This needs to be reported upstream in the property panel project for bpmn.io

Marking as postponed as we need to wait for the upstream resolution.

This has been fixed a while ago.