[keycloak-user] Externally triggered impersonation

Hi there, I have an application (Angular 4 UI + Spring Boot Backend) where I would like to implement user impersonation without going through the Keycloak console. Ideally the power user with the proper impersonation permissions can click a button in the app and then a new windows is being opened in the same application but with the user to impersonate logged in. Is there any example on how to do this or can somebody outline how this would be possible? Thanks, Thorsten