Bug 27855: Implement Koha::Patron::Attribute->to_api_mapping

This patch introduces a mapping to render extended attributes on the
API. As they have an ID, and they will generally be used on the
/patrons umbrella, I removed the borrowernumber on the mapping.

Another option would be to add the field, but make it optional. It
really feels redundant, so I take it out for now.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Koha/Patron/Attribute.pm

@@ -112,6 +112,21 @@ sub description {
     return $self->attribute;
 }
 
+=head3 to_api_mapping
+
+This method returns the mapping for representing a Koha::Patron::Attribute object
+on the API.
+
+=cut
+
+sub to_api_mapping {
+    return {
+        id             => 'extended_attribute_id',
+        attribute      => 'value',
+        borrowernumber => undef,
+        code           => 'type'
+    };
+}
 
 =head2 Internal methods