Generates check digit as per ISO 7064 11,2.
The last character in the ORCID ID is a checksum.
In accordance with ISO/IEC 7064:2003, MOD 11-2,
this checksum must be "0-9" or "X", a capital letter X which represents
the value 10.
See also
Other check:
check_all(),
check_all_person_info(),
check_frontmatter(),
check_structure(),
protocolcheck