Wishlist: add new hooks for acq line items being set as on-order and selector-ready

[Jane Sandberg]

Our current workflow involves marking line items as selector-ready, where our collection development librarian can review them, and then on-order, where our acquisitions person can order them. During slower parts of the year, these people aren't constantly checking the selector-ready and on-order line items. It might be nice if they could receive some email notification when others have line items that are ready for them.