Item barcode should be unique

An item's barcode should be unique. There should be no duplicated barcodes.

The business logic module (mod-inventory) checks for the existence of another item with the same barcode when creating or updating an item and has been rejecting duplicates since mod-inventory version 4.2.0 released May 2017:

• Check for item insert: https://github.com/folio-org/mod-inventory/blob/v4.2.0/src/main/groovy/org/folio/inventory/resources/Items.groovy#L89-L101
• Check for item update: https://github.com/folio-org/mod-inventory/blob/v4.2.0/src/main/groovy/org/folio/inventory/resources/Items.groovy#L124-L135

Duplications can only occur when items are not created via the business logic module (mod-inventory) but directly in the storage module (mod-inventory-storage) or directly in the database (likely via import).

Scope

• Introduce a unique database index on item barcode
• The uniqueness check respects accents and is case insensitive
• All other database indexes for item barcode are removed: non-unique field index, non-unique fullTextIndex, non-unique ginIndex - these indexes are case insensitive but incorrectly ignore accents

Scenarios

Given an item with barcode 12345
When a client attempts to create another item with barcode 12345
Then the request is rejected
And no new item is created

Given an item X with barcode 12345
And an item Y with barcode 34567
When a client attempts to replace the representation of item Y and changes the barcode to 12345
Then the request is rejected
And the representation of item X should not be replaced

Migration
Migration will fail if there are duplicate item barcodes. The "Changes and Required Actions" of

• Juniper Release Notes https://wiki.folio.org/display/REL/R2+2021+%28Juniper%29+Release+Notes
• Kiwi Release Notes https://wiki.folio.org/display/REL/R3+2021+(Kiwi)+Release+Notes

have a note requesting sysOps to check for duplicate item barcodes and remove them before upgrading mod-inventory-storage.