Expose the builder so we can create tier settings

Author: brtrvn

services/settings-service/src/main/java/com/amazon/aws/partners/saasfactory/saasboost/appconfig/ServiceTierConfig.java

@@ -25,6 +25,10 @@ private ServiceTierConfig(Builder builder) {
         this.database = builder.database;
     }
 
+    public static ServiceTierConfig.Builder builder() {
+        return new ServiceTierConfig.Builder();
+    }
+
     public Database getDatabase() {
         return database;
     }