User story

As a user deploying a process model via Cockpit and getting an error because the BPMN is invalid, I want to see the problem details so that I can fix the problems. 

Background

Today we are showing "Communication Error : The application received an unexpected 400 response from the server. Try to refresh the page or login and out of the application."

When the user checked the log file, a more detailed explanation was found: 

ENGINE-16004 Exception while closing command context: ENGINE-09005 Could not parse BPMN process. Errors:
attribute 'messageRef' is required | resource RestTestProcess.bpmn | line 9 | column 74
Invalid 'messageRef': no message with id 'null' found.

AC

• When deploying a process model via Cockpit fails, I can see the reason why the import failed so that I know how to resolve the issue.

Hints

• The REST API response should already contain the details, see https://docs.camunda.org/manual/7.14/reference/rest/overview/#parse-exceptions