Hello Fernando, your question is not really clear to me.
Let me try to explain with my words:
- you want to use a single system user/pwd to interact with the kieserver
- you want to impersonate a user to perform Task management action (so the user "XXXX" claim the task)
If I understood correctly, the way to achieve this is described in the paragraph 16.4 of Development Guide:
1) disable the security settings by using the org.kie.server.bypass.auth.user property.
2) provide a user with sufficient permissions to execute the operation using the query parameter ?user=$USER_NAME. This works, but it's highly discouraged for the security implications. It's better to configure the front-end and the back-end in a SSO domain.