The patch changes workshop_upgrade_module_instances() so that it
processes old workshop records ordered by their id and it keeps the
instances id by using import_record() instead of insert_record().
Thanks to this, there is no mapping of workshop ids needed so the
function workshop_upgrade_workshop_id_mappings() is dropped and all
callers use plain workshop record.
As reported by Trudy Koedooder at http://moodle.org/mod/forum/discuss.php?d=161322
there can be some orphaned grade records without the referenced
assessment. It threw upgrade error. Such grades are now just ignored
during the upgrade.
Aparup Banerjee