monitoring: Support host and service display_name in the EventHistoryQuery

This adds two left joins to the query when selecting host_display_name and service_display_name.
If performance suffers badly, we have to evaluate whether to support the display_name column for displaying
the host and service name in the eventhistory overview.

refs #7843

modules/monitoring/library/Monitoring/Backend/Ido/Query/EventHistoryQuery.php

@@ -33,6 +33,12 @@ class EventHistoryQuery extends IdoQuery
         'hostgroups' => array(
             'hostgroup'             => 'hgo.name1 COLLATE latin1_general_ci',
         ),
+        'hosts' => array(
+            'host_display_name'     => 'h.display_name'
+        ),
+        'services' => array(
+            'service_display_name'  => 's.display_name'
+        )
     );
 
     protected $useSubqueryCount = true;
@@ -114,4 +120,24 @@ class EventHistoryQuery extends IdoQuery
         );
         return $this;
     }
+
+    protected function joinHosts()
+    {
+        $this->select->joinLeft(
+            array('h' => $this->prefix . 'hosts'),
+            'h.host_object_id = eho.object_id',
+            array()
+        );
+        return $this;
+    }
+
+    protected function joinServices()
+    {
+        $this->select->joinLeft(
+            array('s' => $this->prefix . 'services'),
+            's.service_object_id = eho.object_id',
+            array()
+        );
+        return $this;
+    }
 }