add RECURRING_PAYMENT to TransactionSource (#52)

Author: v-rudkovskiy

NetLicensingClient/src/main/java/com/labs64/netlicensing/domain/vo/TransactionSource.java

@@ -65,6 +65,11 @@ public enum TransactionSource {
      */
     SUBSCRIPTION_UPDATE,
 
+    /**
+     * Transaction for recurring payment.
+     */
+    RECURRING_PAYMENT,
+
     /**
      * Transaction for cancel recurring payment.
      */