Specifies collection name in Promotion.java

src/main/java/com/nisum/ascend/promotions/model/Promotion.java

@@ -8,7 +8,7 @@ import org.springframework.data.mongodb.core.mapping.Document;
 
 @Getter
 @Setter
-@Document
+@Document(collection="promotions")
 public class Promotion {
     @Id
     private String id;