This is a backport of the commit integrated as part
of MDL-76055 where we needed the update_enrolments
working to be able to test them. Summary:
- Fixes a typo in table name preventing it to be updated ever.
- Fix outer join that was missing records.
- Stop playing and mixing ids (local and remote).
- Better control which enrolments have to be kept (previously
they were being deleted immediately after creating them).
- Improve the coding style of inserts.
- Modernise the deletions to use sql helper and work win 0..n ids.
Eloy Lafuente (stronk7)
f9e4dcba02