[Extensions] Modify Job Schedule's ScheduleParser to read in the refresh token field

[cwperks]

The ScheduleParser class in Job Scheduler is responsible for reading from schedules from within job definition's registered to the Job Scheduler. Plugin's make Job Scheduler aware of indices they will use to store job definitions and part of those job definitions contains information about the schedule.

The schedule information will also now include a refresh_token which identifies the creator (owner) of the job definition. The ScheduleParser needs to be updated to read this additional field.

[stephen-crawford]

[Triage] This is part of the Extensions project.

[cwperks]

Closing this issue. The user information will not be stored in indices owned by plugins/extensions as an extension is free to override values at any moment. The user info associated with job details should be stored in a secure index where it can be properly protected.