Improve CERN users sync

[ntarocco]

Currently, the sync of CERN users with the local db is halted, because there are conflicts with various primary keys in the DB.
We should improve the sync logic to take into account conflicts based on the CERN person id. We should also harvest the ORCID from the CERN users profiles.

• Evaluate the switch to the AuthZ endpoint, instead of LDAP, so that we can get the ORCID.
• The idea is to create a new common module that can be re-used by various Invenio instances (CDS, ILS, Digital Memory)

[ntarocco]

New module: https://github.com/CERNDocumentServer/invenio-cern-sync/