Added Content by Record ID
^^^^^^^^^^^^^^^^^^^^^^^^^^
Traditionally, Evergreen has supported Added Content lookups by ISBN
only, or (more recently) by one of ISBN or UPC.

This enhancement adds support for Added Content lookups by record
ID, while still supporting the previous URL format for lookups by
ISBN.

The JSPAC and TPAC skins, as well as the web-based Self Checkout
interface templates are updated to use jacket images / cover art by
record ID by default.

By using record identifiers, the Added Content handler has the
opportnity to examine additional identifiers in the bib record.
Currently, these include:

 * ISBN
 * UPC
 * ISSN

Currently, only the OpenILS::WWW::AddedContent::Syndetic provider
makes use of the new identifiers.


Local Content Overrides
+++++++++++++++++++++++
Just as with ISBN lookups, there is support for local overrides in
the form of a file created on disk which short-circuits any external
Added Content lookup.


Apache Configuration
++++++++++++++++++++

The example Apache configs have been updated to support serving
blank.png when added content jacket URLs return a 404. This prevents
"broken image" placeholders in browsers, without requiring a
Javascript onerror handler on each img tag.

The changes are as follows:

In the eg.conf VirtualHost declaration for SSL, add:

[source]
SSLProxyEngine on # required for ErrorDocument 404 on SSL connections

In the eg_vhost.conf file, add:

[source]
<Location /opac/extras/ac/jacket>
        ErrorDocument 404 /opac/images/blank.png
</Location>