Small import improvements

[hornc]

On reimporting existing editions:

• Prevents empty lists being written to the record
  • Closes BWB import bot setting empty 'lc_classification' on many imports #4978
  • Closes ISBN only imports have empty string Library of congress classification set #5671
• Writes any new identifiers (e.g. DNB id) to a matched edition
• Writes OCLC numbers to a matched edition

Previously OCLC number and other identifiers were not added to existing editions if a match was found.

Technical

Testing

Screenshot

Stakeholders

[mekarpeles]

Thank you @hornc!