Add ClusterId__c extracted from alert labels

Change-Id: I5bf731bbba25c863cadf9427226e02d51dabf4b3
Related-PROD: PRODX-4628
diff --git a/sf_notifier/salesforce/client.py b/sf_notifier/salesforce/client.py
index 71ada18..766d3d7 100644
--- a/sf_notifier/salesforce/client.py
+++ b/sf_notifier/salesforce/client.py
@@ -239,6 +239,9 @@
             'Environment2__c': self.environment,
             'Alert_ID__c': alert_id,
         }
+        if labels.get('cluster_id') is not None:
+            payload['ClusterId__c'] = labels['cluster_id']
+
         logger.info('Try to create case: {}.'.format(payload))
         try:
             self.metrics['sf_request_count'].inc()