As a user, I want my Zotero metadata to include the PPA item URL so that I can easily link back to and cite an item I found on the PPA.

[mnaydan]

On #379 RSK discussed using pymarc to tweak the MARC records before we serve them out. We could do this to correct information like page count or volume but a potentially more important improvement is that we could set the PPA item url in the MARC record, in addition to or instead of the source url that's there now.