Added Coupon Based Discounts

[Safemood]

This PR implements coupon-based discounts, allowing users to apply various types of coupons to their cart items. It includes tests covering scenarios such as applying time-limited coupons, single-use coupons, restricted user coupons, and limited usage coupons. Additionally, the README file has been updated with code examples demonstrating how to utilize different types of coupons.

Coupon Examples

use Safemood\Discountify\Facades\Coupon;


// Time-Limited Coupon

Coupon::add([
    'code' => 'TIMELIMITED50',
    'discount' => 50,
    'startDate' => now(),
    'endDate' => now()->addWeek(),
]);

$total = Discountify::setItems($items)
    ->applyCoupon('TIMELIMITED50')
    ->total();

// Single-Use Coupon

Coupon::add([
    'code' => 'SINGLEUSE50',
    'discount' => 50,
    'singleUse' => true,
    'startDate' => now(),
    'endDate' => now()->addWeek(),
]);

$total = Discountify::setItems($items)
    ->applyCoupon('SINGLEUSE50')
    ->total();

// Restricted User Coupon

Coupon::add([
    'code' => 'RESTRICTED20',
    'discount' => 20,
    'userIds' => [123, 456], // Restricted to user IDs 123 and 456
    'startDate' => now(),
    'endDate' => now()->addWeek(),
]);

$total = Discountify::setItems($items)
    ->applyCoupon('RESTRICTED20', 123) // Applying to user ID 123
    ->total();

// Limited Usage Coupon

Coupon::add([
    'code' => 'LIMITED25',
    'discount' => 25,
    'usageLimit' => 3, // Limited to 3 uses
    'startDate' => now(),
    'endDate' => now()->addWeek(),
]);

$total = Discountify::setItems($items)
    ->applyCoupon('LIMITED25')
    ->total();