Update issue by using Jira-Fields as asset attributes

[Gerrit Wahlers]

We have a object scheme called "Zuständigkeitsbereiche". 

After a issue is created, we can assign a "Zuständigkeitsbereich" (area of responsibility) to an issue. This object has attributes like assignee, component, keyword, impact, participants and watchers.

Watchers and participants are multi-user-fields.
Assignee is a single user field.
impact, keyword and component are text fields.

After a "Zuständigkeitsbereich" has changed a automation has to update the pendant jira-fields.

Zuständigkeitsbereich.participants add to issue.request participants
Zuständigkeitsbereich.assignee set to issue.assignee
Zuständigkeitsbereich.watchers add to issue.watchers
Zuständigkeitsbereich.impact set to issue.impact
Zuständigkeitsbereich.keyword add to issue.keyword

For request participants we already tried the KB-article Add Users from Asset attribute to request participants | Jira | Atlassian Documentation, but we got an error.

Somebody here who can help me out?