Add support for Preferred Borrowers that applies to checkouts as well as holds
In larger consortia, it's very impractical to have granular patron codes per library or branch. Our resident patron codes are shared by all the libraries, but this creates some problems for certain materials that libraries can't reasonably share. The Preferred Borrower hold limit can help with this, but it puts the control of circulating restricted materials on the staff. If a Preferred Borrower setting could apply to checkout of certain materials the way holds can be limited with Preferred Borrower settings, staff would not have to struggle with overrides or demanding patrons from the next town over.