Default likes parameter to 0 when creating a Daily (#19)

backend-services/feed-service/app/models/Daily.scala

@@ -26,7 +26,7 @@ object Daily {
         userId: ObjectId,
         questionId: ObjectId,
         content: String,
-        likes: Int,
+        likes: Int = 0,
         timeout: Int = 4
     ): Daily = {
         val daily: Daily = Daily(None, userId, questionId, content, likes)