Comment 6 for bug 1814966

Here's a branch that adds a check for an invalid barcode if "Use Checkdigit" is checked, and will show a message and prevent saving if the check fails, similar to the way the check for a duplicate barcode functions. The code for the barcode validity check is borrowed from the Angular patron interfaces.

https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/jwoolford/lp1814966-warning-for-invalid-barcode

A note for committers: There are now two commits on this branch that will need to be squashed. If this fix is implemented along with the fix for 1998494, they will conflict, so probably easiest to apply the minor fix from that bug/branch here before merging if both are accepted.