Requirement:  When a user edits a MARC authority record,  only allow one 010 field since 010 is a not repeatable field (https://www.loc.gov/marc/authority/ad010.html) 

Error message to display when user attempts to save multiple 010 fields - Cannot save multiple 010 fields.

Scenario 1

Given a user edits a MARC authority record 

AND s/he adds a MARC field 010 

AND a MARC field 010 already exist

WHEN she clicks Save button

THEN display an error message - Cannot save multiple 010 fields.

Scenario 2

Given a user edits a MARC authority record 

AND s/he adds a MARC field 010 

AND a MARC field 010 does not exist

WHEN she clicks Save button

THEN save the record