User task

Number of APIs: 4

1. Update a user task PATCH {{zeebeApiBaseUrl}}/v1/user-tasks/:userTaskKey

2. Assign a user task POST {{zeebeApiBaseUrl}}/v1/user-tasks/:userTaskKey/assignment

3. Complete a user task POST {{zeebeApiBaseUrl}}/v1/user-tasks/:userTaskKey/completion

4. Unassign a user task DELETE {{zeebeApiBaseUrl}}/v1/user-tasks/:userTaskKey/assignee