Set a timer in loleaflet 15 minutes before access token expiry
date (access_token_ttl value) to prompt the user to save and
refresh the session.
Change-Id: I98c3e47c9b7031e29e002f653d488747b9c17df8
Reviewed-on: https://gerrit.libreoffice.org/31381
Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>