PLT-7177: Change the default email frequency to 15 minutes if batching is enabled on the server. (#7036)

* PLT-7177: Found default preference that needs to be changed

* PLT-7177: Front end behaves as desired

* PLT-7177: Changed default batching interval on server side

* PLT-7177: Added unit tests for new default interval

* PLT-7177: Removed unused import

* PLT-7177: Renamed constants to increase clarity

app/email_batching.go

@@ -140,13 +140,14 @@ func (job *EmailBatchingJob) checkPendingNotifications(now time.Time, handler fu
 		// get how long we need to wait to send notifications to the user
 		var interval int64
 		if result := <-pchan; result.Err != nil {
-			// default to 30 seconds to match the send "immediate" setting
-			interval, _ = strconv.ParseInt(model.PREFERENCE_DEFAULT_EMAIL_INTERVAL, 10, 64)
+			// use the default batching interval if an error ocurrs while fetching user preferences
+			interval, _ = strconv.ParseInt(model.PREFERENCE_EMAIL_INTERVAL_BATCHING_SECONDS, 10, 64)
 		} else {
 			preference := result.Data.(model.Preference)
 
 			if value, err := strconv.ParseInt(preference.Value, 10, 64); err != nil {
-				interval, _ = strconv.ParseInt(model.PREFERENCE_DEFAULT_EMAIL_INTERVAL, 10, 64)
+				// // use the default batching interval if an error ocurrs while deserializing user preferences
+				interval, _ = strconv.ParseInt(model.PREFERENCE_EMAIL_INTERVAL_BATCHING_SECONDS, 10, 64)
 			} else {
 				interval = value
 			}