Add latency metric for notification service

This MR is to create custom metric for event notification latency. The latency is the time between the message is sent into message bus until the first successful attempt to deliver the message to subscriber. The response time from the subscriber is not included.

In the customDimension of the metric, we included correlation id, data partition id and topic name the message belongs to.

Issue: #126

notification-core/src/main/java/org/opengroup/osdu/notification/api/PubsubEndpoint.java

@@ -74,7 +74,7 @@ public class PubsubEndpoint {
         String notificationId = this.pubsubRequestBodyExtractor.extractNotificationIdFromRequestBody();
         String pubsubMessage = this.pubsubRequestBodyExtractor.extractDataFromRequestBody();
         Map<String, String> headerAttributes = this.pubsubRequestBodyExtractor.extractAttributesFromRequestBody();
-        HttpResponse response = notificationHandler.notifySubscriber(notificationId, pubsubMessage, headerAttributes);
+        HttpResponse response = notificationHandler.notifySubscriber(notificationId, pubsubMessage, headerAttributes, true);
         if (!response.isSuccessCode()) {
             this.log.error(NOT_ACKNOWLEDGE + response.getBody());
             return new ResponseEntity<String>(NOT_ACKNOWLEDGE, HttpStatus.valueOf(response.getResponseCode()));