This story covers the download transaction for audiobooks. UI will be covered in a separate story: SIMPLY-1052

Refer to Step 5 of main flow for patron adjusts settings: https://confluence.nypl.org/display/SIM/Patron+finds%2C+borrows%2C+plays%2C+and+adjusts+settings+for+audio+books+in+SimplyE#Patronfinds,borrows,plays,andadjustssettingsforaudiobooksinSimplyE-4.PatronadjustssettingsonaudiobooksinSimplyE

Acceptance Criteria

• Given an audiobook is borrowed
• Then loading of audiobook chapters begins immediately
• And progress of download is available to be displayed on front-end