Rename fields (#84)

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## **What the change does.**

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## **Does this change break backwards compatibility?.**

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Author: ioannis-kody

src/main/proto/com/kodypay/grpc/pay/v1/pay.proto

@@ -108,9 +108,9 @@ message PayResponse {
 
   message RefundDetails {
     string payment_id = 1;
-    optional string psp_reference = 2; // Might not have a PSP yet reference if pending
+    optional string refund_psp_reference = 2; // Might not have a PSP yet reference if pending
     string payment_transaction_id = 3;
-    string total_paid_amount = 4;
+    string refund_amount = 4;
     google.protobuf.Timestamp event_date = 5;
     optional string terminal_id = 6;
   }