BibMerge: prevent loss of DOI when merging records
- Check that no managed DOIs are lost when merging records.
- Check that no duplicate DOIs are created when merging records.
- Behaviour regarding deletion of managed DOIs when merging can be tuned with CFG_BIBEDIT_INTERNAL_DOI_PROTECTION_LEVEL. (closes #1446)
Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Acked-by: Javier Martin Montull <javier.martin.montull@cern.ch>