Include parts label when sorting copies in the public catalog
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The list of copies on the record details page now includes
the part label in the default sort order.

Specifically, copies are now sorted by (in order), org unit, then
call number, then part label sortkey, then copy number, and
finally barcode.

Previously, the hierarchy was org unit, then call number,
then copy number, and finally barcode