Bug 32256: Handle batch error messages better

Bug 32256: Handle batch error messages better

This enhancement modifies the self-checkout script to better handle 'impossible' and 'needs confirmation' checkout messages.

Test with a combination of barcodes that would invoke these messages, for example:
- impossible: barcode doesn't exist
- impossible: barcode is for a 'notforloan' item type
- impossible: debt
- needs confirmation: barcode already checked out, i.e. confirm renewal

Include barcodes that should have successful checkouts too.

Also, test with the following sysprefs:
- BatchCheckouts: enabled
- BatchCheckoutsValidCategories: none selected

Confirm SCO does not have a multi-line text area for more than one barcode, and doesn't accept more than one barcode.

Signed-off-by: Andrew Fuerste Henry <andrewfh@dubcolib.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Andrew Fuerste Henry <andrewfh@dubcolib.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>