refactor: Delete legacy openapi.* packages and old filter/wrapper classes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thced

src/main/java/com/retailsvc/http/BodyHandler.java

@@ -13,8 +13,4 @@
 public interface ExceptionHandler {
 
   void handle(HttpExchange exchange, Throwable t) throws IOException;
-
-  default void handleException(HttpExchange exchange, Exception e) throws IOException {
-    handle(exchange, e);
-  }
 }