fix(router): added validation to check total orderDetails amount equal to amount in request (#2965)

Co-authored-by: Sahkal Poddar <sahkal.poddar@juspay.in>

crates/router/src/core/payments/helpers.rs

@@ -3686,3 +3686,22 @@ pub async fn get_gsm_record(
         })
         .ok()
 }
+
+pub fn validate_order_details_amount(
+    order_details: Vec<api_models::payments::OrderDetailsWithAmount>,
+    amount: i64,
+) -> Result<(), errors::ApiErrorResponse> {
+    let total_order_details_amount: i64 = order_details
+        .iter()
+        .map(|order| order.amount * i64::from(order.quantity))
+        .sum();
+
+    if total_order_details_amount != amount {
+        Err(errors::ApiErrorResponse::InvalidRequestData {
+            message: "Total sum of order details doesn't match amount in payment request"
+                .to_string(),
+        })
+    } else {
+        Ok(())
+    }
+}