fix: resolve SonarQube code quality issues

[Fauxirius]

SonarQube Triage Summary

This PR addresses code quality issues identified by SonarQube.

Fixed Issues

1. S106: Replace this use of 'System.out' with a logger

• Type: CODE_SMELL
• Severity: MAJOR
• File: JU4/src/main/java/com/javatechie/pm/api/service/OrderService.java

Before:

	private int addDiscount(OrderRequest order) {
		System.out.println("called...");
		int price = order.getPrice();

After:

package com.javatechie.pm.api.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
// ...

@Service
public class OrderService {

    private static final Logger logger = LoggerFactory.getLogger(OrderService.class);
    // ...
	private int addDiscount(OrderRequest order) {
		logger.info("called...");
		int price = order.getPrice();

Verification Notes

• Verified that System.out.println was replaced with a standard SLF4J logger.
• Ensured appropriate imports (org.slf4j.Logger, org.slf4j.LoggerFactory) were added.
• Added a static final logger instance to the OrderService class.