do not issue refunds for non-refundable payment types

bubble-server/src/main/java/bubble/model/bill/PaymentMethodType.java

@@ -13,4 +13,6 @@ public enum PaymentMethodType {
 
     @JsonCreator public static PaymentMethodType fromString(String v) { return enumFromString(PaymentMethodType.class, v); }
 
+    public boolean refundable() { return this == credit; }
+
 }

bubble-server/src/main/java/bubble/service/bill/StandardRefundService.java

@@ -40,6 +40,10 @@ public class StandardRefundService extends SimpleDaemon implements RefundService
         for (AccountPlan accountPlan : pendingPlans) {
             try {
                 final AccountPaymentMethod paymentMethod = paymentMethodDAO.findByUuid(accountPlan.getPaymentMethod());
+                if (!paymentMethod.getPaymentMethodType().refundable()) {
+                    log.info("process: not issuing refund for plan "+accountPlan.getUuid()+" because paymentMethodType="+paymentMethod.getPaymentMethodType());
+                    continue;
+                }
                 final CloudService paymentCloud = cloudDAO.findByUuid(paymentMethod.getCloud());
                 final PaymentServiceDriver paymentDriver = paymentCloud.getPaymentDriver(configuration);
                 paymentDriver.refund(accountPlan.getUuid());