BibAuthorID: add_cname_to_hepname_record()
- Introduces a new API add_cname_to_hepname_record() to automatically schedule a BibUpload bibtask to append a new person ID to a given record.
- Moves retry_mkstemp() from bibdocfile to shellutils so that other modules can use it.
Signed-off-by: Samuele Kaplun <samuele.kaplun@cern.ch>