fix: create new user task form only if user task form referenced

[philippfromme]

• does not create a new form definition, instead it only creates a new user task form and references it
• does not create a new user task form if there is no existing user task form already referenced by another form definition

Related to camunda/camunda-modeler#4658

[abdul99ahad]

Works as expected. Just a quick question. When you copy and paste the user task with linked form , it will create a new form with the same form ID? or will it reference the same form?

[barmac]

Works as expected.

[nikku]

@philippfromme This is pending integration 🙃