Add Product record to represent product details

src/main/java/com/example/productaffinity/domain/model/Product.java

@@ -0,0 +1,7 @@
+package com.example.productaffinity.domain.model;
+
+import java.math.BigDecimal;
+
+// Represents a product detail
+public record Product(String id, String name, BigDecimal price, boolean availability) {
+}