I can access the assignee of a completed user task or user form

[saig0]

Is your feature request related to a problem? Please describe.
I have a process with a sequence of user tasks. The user tasks don't have a fixed assignee, either unassigned or with candidate users/groups. The user who completed the first user task A should work on the follow-up user tasks B and C.

Currently, I can't use the user of the completed task A as the assignee of task B. The user needs to assign themself.

A similar problem exists if the process is created by a user form in Tasklist. In this case, the user who filled out the user form should work on the next task A.

Describe the solution you'd like
I can access the assignee of a completed user task and store it in a process variable to use it as the assignee for a follow-up user task.

💡 Idea: I can access the assignee of the user task in the output mapping of the user task. For example, by using the expression context (ref): = camunda.user_task.assignee.

For user start forms: I can access the user of a completed user start form and store it in a process variable to use it as the assignee for a follow-up user task.

Describe alternatives you've considered

• The user needs to assign themself every time - Error-prone + a lot of clicks
• Use the Tasklist API to fetch the completed user task - Complicated + pollute the process

Additional context
This feature is relevant for user-driven/-focused processes, for example, in an end-to-end release process.