dspace/config/spring: add index for CGIAR center subject

This combines all CGIAR center subjects (cg.subject.*) into a sin-
gle index that we can search on and make clickable from the item
page.

Author: alanorth

dspace/config/spring/api/discovery.xml

@@ -200,6 +200,7 @@
                 <ref bean="searchFilterImpactPlatform" />
                 <ref bean="searchFilterCrpSubject" />
                 <ref bean="searchFilterSubject"/>
+                <ref bean="searchFilterCgiarCenterSubject" />
                 <ref bean="searchFilterActionArea" />
                 <ref bean="searchFilterImpactArea" />
                 <ref bean="searchFilterSDG" />
@@ -3015,6 +3016,15 @@
         <property name="sortOrderFilterPage" value="COUNT"/>
     </bean>
 
+    <bean id="searchFilterCgiarCenterSubject" class="org.dspace.discovery.configuration.DiscoverySearchFilter">
+        <property name="indexFieldName" value="subjects"/>
+        <property name="metadataFields">
+            <list>
+                <value>cg.subject.*</value>
+            </list>
+        </property>
+    </bean>
+
     <bean id="searchFilterSponsorship" class="org.dspace.discovery.configuration.DiscoverySearchFilterFacet">
         <property name="indexFieldName" value="sponsorship"/>
         <property name="metadataFields">