[keycloak-user] Schedule background jobs as user

So we've done a lot of work on our migration to keycloak but still have a few holes that are using another authentication system. We are using Wildfly10 along with the keycloak subsystem. The last real blocking issues is trying to schedule background tasks on behalf of a user using quartz. We've tried using impersonation role and mocking out the impersonation workflow that a browser does, it was fairly complicated and did not work very well. Service accounts don't seem to fit this scenario either as service accounts seem to be for performing client specific actions. We considered storing offline token's on behalf of users but the thing is users might not log in for years after scheduling their job. We need to set the Context and Principle to be the user who we are performing background tasks on behalf of. Is there a recommended way of doing this that has been tested by others? I'm sure we aren't the only company who schedule tasks on behalf of users.