added basic strcture for the callbackapi

src/main/java/com/billpaymentservice/bbps/serviceImpl/PaymentServiceImpl.java

@@ -398,6 +398,24 @@ public class PaymentServiceImpl implements PaymentService {
 	        throw new CustomException("Invalid JSON received from API");
 	    }
 	}
+
+	@Override
+	public ResponseModel handlePaymentIntiateCallback(TransactionStatusResponse transactionStatusResponse) {
+
+		LOGGER.info("Recived Call Back from FetchBillValidateResponse: {}", transactionStatusResponse);
+	    if(transactionStatusResponse.getGeneralResp().getStatusCode().equals("200")) {
+	      
+	     }
+	    else {
+	   	 LOGGER.info("Bill Fetch Callback Failed with Status: {}", transactionStatusResponse.getGeneralResp().getStatus());
+	   	 
+	    }
+	    
+	    return new ResponseModel("CallBack Recieved Successfully",
+	   			"200",
+	   			200,
+	   			"");
+	}
 }
 	/*  PollBack logic for the fetchTxnByTxnId API
 	 * @Override public ResponseModel fetchTxnByTxnId(BillFetchByBillIdRequest