BAM-284: add idempotency support for ordering sdk (#79)

**Associated JIRA tasks**
BAM-284: https://kodypay.atlassian.net/browse/BAM-284

**What the code does.**

Introduce intempotency_uuid to the update status and refund methods.

**Does this code change break backwards compatibility?.**
Yes, I have change the order of the fields UpdateStatus endpoint and
RefundStatus. However, they are not used by any customer yet. Will
inform Blackfire integration engineer who is current implementing the
updateStatus endpoint once this is release.

Also, I will create a quick fix if it breaks kp-core.

Author: HaitaoDan

src/main/proto/com/kodypay/grpc/ordering/v1/order.proto

@@ -54,6 +54,9 @@ message UpdateOrderStatusRequest {
 
   // New status for the order.
   OrderStatus new_status = 3;
+
+  // UUID idempotency key. Will be generated by client.
+  string idempotency_uuid = 4;
 }
 
 message UpdateOrderStatusResponse {
@@ -73,6 +76,8 @@ message RefundItemRequest {
   repeated RefundItem items = 3;
   // Optional reason for the refund.
   optional string reason = 4;
+  // UUID idempotency key. Will be generated by client.
+  string idempotency_uuid = 5;
 
   message RefundItem {
     string order_item_id = 1;
@@ -98,6 +103,8 @@ message RefundOrderRequest {
   string order_id = 2;
   // Optional reason for the refund.
   optional string reason = 3;
+  // UUID idempotency key. Will be generated by client.
+  string idempotency_uuid = 4;
 }
 
 // Response for refunding an entire order.