Hidden courses that have remained unmodified in a month should not be skipped from backup

The scheduled back up code "Skip backup of unavailable courses that have remained unmodified in a month"

However, it uses the timemodified field in the course table to check if this course has been modified. This field only ever changes when a course setting is changed.

So we have had incidences where a teacher has hidden a course and then worked extensively on building it for weeks, in preparation for the next period. The course is never backed up. We have had to rebuild entire instances of Moodle using file and database backups, to restore lost courses.

We therefore comment out this code. We would like an improvement to either remove this code or adapt it to check if a course really has been modified.